Just throwing in my two cents here, trying to get back into CDDA again.
For an 8/8/8/8 survivor Alpha offers the best stat boosts out of all the post-threshold mutation trees with no appreciable drawbacks. Fast Metabolism won’t matter by the time you can make Alpha Mutagen with all the food you’ll have stockpiled, Nausea actually let’s you throw up on demand with no real drawback, and Weakening does literal scratch damage that sleeping regularly will have you not even notice. In exchange you get +7 ‘Prime’ versions of all four stats, which is equalvient to the ‘Insanely’ prefix most post-threshold mutants get for only one stat. You also get Good Hearing, Weak Scent, Pretty, Very Little Sleep and Robust Genetics along the way.
The only drawback is you don’t get any of the better extrasensory mutations like night or infrared vision. I’d recommend someone planning to go Alpha take some Troglobite mutagen first thing after you post-threshold. Ideally you’ll have gotten Robust Genetics either at char creation or due to shooting up for Alpha. Troglobite has some of the best pre-threshold mutations, several of which directly counter negative Alpha mutations and can give you both full night and infrared vision with minimal drawbacks. But it really isn’t worth going post-threshold with, so mutate and purify to your heart’s content because Troglobite mutagen only needs chunks of meat to make. Plus it has no stat changing mutations, so it won’t mess with your Prime mutations like most other trees.