Light sensitive is a big problem, still.
Having the perk Robut genetic help a lot when you want a “good” mutation, because it’s less likely you will get a “bad” mutation whenever it could happen.
One thing you could do, but cost some time :
Pick a lot of mutagen (craft), and purifer (not hard to found, lab).
Do so you can craft mutagen into beast mutagen, then drink untill you get all what you want.
Then pick a purifer : if it take away light sensitive, go with it. If it take away other annoying stuff, re drink. And if it take away strenght & co, pick another beast mutagen, and go step purifer.
About the strengh mutation,
saying there is 4 rank of this perk : You need 1 to get to 2, 2 to get to 3, etc.
If game pick 3 and …
You have 0 : you go at 1.
You have 1 : You go at 2.
You have 2 : you go at 3.
You have 3/4 : it won’t pick 3 in this case.
In case of tail, you need the base . same, if game pick stuffy tail, you will get base if you didn’t have it before. And if game pick another tail while you have fluffy, it will REMOVE your old tail for the new one.