Two links:
https://runemate.gitbook.io/runemate-documentation/getting-started/runemate-user-guide
https://runemate.gitbook.io/runemate-documentation/getting-started/runemate-user-guide/importing-jagex-characters
Launch your RuneLite clients from RuneMate itself, rather than from the Jagex Launcher.
More info here:
https://www.runemate.com/community/threads/how-to-add-game-accounts-to-the-runemate-client.25627/
Try just grabbing a fresh copy of the installer from the website and trying again. Install4J is the thing that is crashing and that is not our software.
You can use Nord but there's a couple of things to be aware of, firstly it's best if you use an IP from a western country, and second you need to have the VPN open and enabled for you ever open a RuneMate or RuneLite window - that means it's best to do a clean restart before botting.
You'll need to mention specific bots - many of us have already started implementing this practice in our bots but some are slow to catch up (or simply unaware that this is the best thing to do).
Almost all premium bots feature a trial which should be used to configure settings etc.