Currently only Windows is supported, but I would like to support more.
If you are proficient with coding in Linux or Mac and would like to help out, please let me know.

No, all the data stays entirely on your system. The only web requests are to check for updates, but this can be disabled with the --offline flag.

No, the total count of keys pressed is recorded, but not the order, and you can fully disable the keyboard tracking if it makes you more comfortable.

It's an option in the menu: Preferences > Startup > Start MouseTracks at Login.

If you were to download and run a never version while this setting is enabled, then it will automatically update the startup path for you.

Yes, if an application is being tracked, then the bounds will be set to its window geometry.

Only raw mouse data is recorded. If the mouse gets pulled towards the middle of the screen, it'll record exactly that and won't attempt to compensate.

Admittedly nobody is asking this question, but it's literally the reason I built the first version back in early 2017.

Change resolution and everything breaks, and it can't cope with too much data.
Too much tracking results in black bars: https://www.reddit.com/r/MouseMovement/comments/6brmhm/4_hours_56_minutes_of_well_damnit_i_forgot_to
Too many clicks results in a red screen: https://assets2.razerzone.com/images/synapse/3c7171cb5dc63e1dbbce93bfc17553b9-starcraft_ii_mouse_clicks_tlo_all.png

It's meant for short term tracking only and doesn't save raw data.

Never used it, but had I learned about it a decade ago I almost certainly would be.
On face value, it seems more built around "raw stats", and MouseTracks is a mix of art and stats. It also has a paywall.

Yes, it will combine and render to the most common resolution. Specific resolutions can be turned off if required.

I'm aware that the default heatmap is the typical not-so-friendly "jet" heatmap, but it was chosen as it looked nice.
I've tried to include a range of colour maps to pick from, but you can also define your own.

Yes, but not massively. If it's something you're worried about, minimise the GUI to prevent it from updating.

Most profiles are just a few MB, a large one can hit 25MB.

Average usage will put it somewhere between 500MB - 1GB.