I have just done this merge 3 into 1 thing. Seems to work fine ☺️ But be careful: this is advanced stuff. It's not very hard, but you need to know, what you are doing...
I noticed, that stock management is a bit tricky, if you used "share_stock" before 🫣 IMO what you have to do in stock_available table:
set id_shoup_group = 0
set id_shop = ID_OF_YOUR_SHOP (note: this can differ from 1)
Additional Edit:
you should also check ps_configuration table similair to stock_available table