The description reads:

This mod is in early alpha. In my current playthrough I can finish the first tier of science packs (about 200h taking it casually). For the recipes unlocked during first tier there are no plans to change anything (except maybe change some ratios). All recipes comming after allready exist, but might not be reachable through tech tree.

I am now almost finished with Tier 1 science packs and about to start the second tier of science packs (like Automation science 2 which is e.g. needed for Space science if I saw that correctly).

Is it worthwhile to start with Tier 2 already or should I rather wait / pause my run, given the description above? Would hate to change my factory significantly due to major changes in recipes for science 2.

I'd say go for it. I'm most of the way through the second tier. There have been a few changes, but nothing that required me to rebuild huge sections of my base.

Most parts of the second tier are allready in place. Nuclear, space, computer and cryogenic science pack are not done.

Thank you! Seems there is enough to do for the foreseeable future then :-)