Skyrim and WoW absolutely are high-motion and 1500 will likely be a bit low; 2000 would be more appropriate for better image fidelity. It's all about how much the picture on the screen moves around/changes.
Anything first-person or third-person includes large amounts of overall on-screen motion (just turning around, moving forward/back, etc updates the ENTIRE screen, and usually quite dramatically compared to the previous frame). PoE may be a good bit less, and I can't speak on Runescape as I haven't played it and most who recommend it seem to be joking (given the number of Kappa that tend to follow).

Yes, Lanczos is very low impact if you aren't playing on an ancient paperweight (Core2Duo or something).

Why you should NOT be streaming at 1080p

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Streaming myths debunked #1

“I want to stream at 1080p60fps like Shroud.”

We see this everyday. We understand that you want to emulate top creators but more often than not, new streamers will end up disappointed and frustrated because they simply do not meet the requirements to output at the highest quality available — resulting in “lag”, poor game performance, stuttering and a number of common issues we see everyday. I invite you all to check on xQc or Pokimane’s early streams and compare the quality they have today with what they started with. 1080p 60fps is not a requirement to produce good entertainment and content for viewers, so do keep that in mind folks, start small, and improve gradually.

Streaming at the highest resolution may be the biggest mistake you ever make at the start of your streaming journey, here’s why:

Reason #1: Hardware

For starters, you need to be aware of how good your PC is. The big streamers all have the latest gear available. Their gaming PC probably has a 3080/3090 graphics card, the latest generation of CPU with the highest number of cores. Oh and quite a few of them have 2 PCs: one for gaming, and one who’s sole task is to encode and produce the highest quality stream/recording.

I bet 95% of streamers right now, including you, are on a single PC setup. Nothing wrong with that, but it is important to keep realistic expectations as there is no magic that can be done in terms of making your PC better than it is.

Quick Tip:

For a smooth streaming experience, we recommend an NVIDIA GPU from at least the Pascal generation (10 series) as its NVENC capabilities lets you stream more efficiently whilst minimizing game performance impact. A modern 4-core CPU from Intel or AMD released within the last 4 years will be fine for running your games and we only encourage buying enthusiast-grade CPUs if you already have a specific need for them or have enough experience in dealing with high-end components. Also, make sure you have at least 8 GB of RAM as that’s the ideal minimum that Windows 10 would need but we recommend 16 GB of RAM for safety.

Reason #2: Upload Bandwidth

Not all internet service providers are created equal. It doesn’t matter if your rig has the latest components money can buy; if your internet upload can’t push the bitrate required for a 1080p 60fps stream, then you need to adjust your expectations.

If you don’t know what bitrate is: it is an option within streaming software like Gamecaster that essentially decides “how much information should I send within a time frame”. In this particular instance, we’re talking about video bitrate. The more information there is to send, the higher you need your bitrate to be set.

For a very simplified explanation, if you manually set your bitrate to 5000 in Gamecaster, you will need at the very least 5Mbps upload speed from your bandwidth. Other factors such as open websites and devices in the household will obviously affect that so if you are barely at 5Mbps upload on your bandwidth test, you should lower the bitrate to something like 3000.

More importantly, the higher you set your bitrate, the better the connection of the viewers need to be to watch your stream at maximum quality. So it would be wise to set your bitrate modestly, unless the platform you’re streaming to has transcoding enabled by default (more on that later).

Quick Tip:

General rule of thumb for manually setting bitrate is:

• 1080p, 60fps > your bitrate should be 4,500 to 6,000 kbps
• 1080p, 30fps > your bitrate should be 3,500 to 5,000 kbps
• 720p, 60fps > your bitrate should be 3,500 to 5,000 kbps
• 720p, 30fps > your bitrate should be 2,500 to 3,500 kbps

Also if you’re using Gamecaster, you can just use the Automatic setting so you don’t have to worry about figuring out which settings work with your upload speed.

Reason #3: Twitch Transcoding

When you watch a big streamer on Twitch, you have the option to select between multiple resolutions such as 480, 720 and 1080 in most cases. However, this is only for Twitch Affiliates and Partners and if you are not a partner, viewers will not have an option and will be forced to view your stream at whatever output you set on the streaming software.

So coupled with the Bitrate and Resolution information from above, if you try to stream at 1080p30fps with a 5k bitrate, some viewers will be forced to 1080p and will simply not have the bandwidth to view your stream and will end up with a constantly buffering experience.

In summary, by insisting on streaming at 1080p without being a Twitch Partner, you are limiting the number of viewers that can potentially tune in.

Twitch and other platforms have yet to release any data on the share of viewers watching 1080p, but a quick glance on the web and surveys will tell you that most people don’t actually watch 1080p streams..

Quick tip: For the best balance, we recommend 720p30fps at 2500–3500 bitrate.

Reason #4: High Motion Games

When playing games that have a lot of movement on screen such as first person shooters, there’s a tendency for the stream to encounter blurriness and “artifacting” where the video looks like it’s broken. You will usually find this happening on streams that are broadcasting at 1080p 60fps. Even if they set a bitrate of 6000 kbps, there is simply not enough space to fit all the information happening on screen when flicking around very fast.

Quick Tip:

Setting a lower resolution or lower fps at the same bitrate would result in a better quality stream overall. At 6000 kbps, a 1080p 30fps stream or a 720p 60fps stream would be better than forcing a 1080p 60fps stream.