It was suggested before here, closing as a duplicate:

https://tweaker.userecho.com/topics/970-add-support-for-horizontal-scroll-wheel

I'm not familiar with this problem. What's your Windows version? Are you using other Windows customization tools? Which 7+ Taskbar Tweaker options are you using? Does the problem happen even if all of the tweaker's options are disabled?

Also, there's this Windows bug, make sure that's not what you're seeing, and try the workaround:

https://superuser.com/questions/61833/windows-7-taskbar-icon-highlight-sticks

Regarding the second item, check out the Taskbar Clock Customization Windhawk mod. Specifically, check out the "Text spacing" configuration.

Im always with spotify open, a chrome window with 1 video open (which I put on my second monitor) or a chrome window with my app preview open, but it’s “hard” finding them on a taskbar that has, like, 15 apps.

What you can do for now is use the "Don't group pinned items" option, then you'll always have your pinned icons at the left side of the taskbar, always at the same place.

This functionality is implemented in the Taskbar Scroll Actions Windhawk mod.

This functionality is unrelated to the taskbar, and won't be implemented as part of 7+ Taskbar Tweaker. Perhaps somebody will implement it as a Windhawk mod some day.

Done in v5.14.2.

Fixed in v5.14.2.

Please try the newly released beta version, v5.14.1.4, and let me know whether it works. It can be downloaded here. If all is well, I'll release a non-beta version with the fix in a couple of days.

Then it sounds like an issue with the app. Perhaps it destroys its window on logout, and creates a new one on logon, so it's created at the end.

And you're welcome :)