I add pectic enzyme to all fruit wines, as it's a low cost product and doing so eliminates a potential additional step later on. It helps with fruit breakdown, although I don't know if it does more than freezing alone may.
Go cautious on acid additions, as it's much easier to add more later than to take some out. I make this statement often, tongue-in-cheek, but it is literally true.
I make final adjustment to acid base upon taste. I go light, adding a bit at a time, stirring well, then letting the wine rest a few days for the acid to integrate.
The 2020 Sauvignon Blanc my son & I made is a good example. A month before bottling we tasted, and it came across flabby. It was good (great fruit flavor) but lacked a zing. It was aged in a pair of 3 gallon carboys, and we added 1/2 tsp acid blend to each, and waited a week. The difference was remarkable. We considered adding more acid, but decided to sit pat. Five months later, EVERYONE wants a bottle ... and I only
have had 15, now down to 12 ...
This is very subjective, as David pointed out. It would be great if there were formulas we could use to decide on adjustments, but wine is far too complex. We can make some decisions on the numbers, but overall? It's subjective -- you need to use your experience -- which takes time and practice to develop.