Easy-breezy hidden synonym theme, WHIFF, FAN, STRIKE all relating to striking out. I did check-swing on this theme concept at first, given that WHIFF and STRIKE are a single swing and miss, while FAN is a strikeout.

Then I realized that there are three synonyms … and in total, they're more or less three strikes, which equals GO DOWN SWINGING! Clever. (The puzzle, that is, not me, given how long it took me to figure that out. Probably ought to pull me for a reliever.)
John threw some heat in his bonus material, HALFLIFE, UNDERWORLD, ROSE GOLD, and PREALGEBRA good to great. With four themers — even if they're longish — it's almost always possible to work in four long bonus downs in staggered positions. Easy formula: spread out your four themers, spread out your four long downs, test liberally to make sure every section is fillable, and you're done!
It's not that easy of course, but it's a tried and true formula.
I also liked the changeup, John using a couple of long bonuses in the across direction. AD SLOGAN and LARGESSE are great entries. Most constructors don't do this type of thing because it can put a ton of strain on a grid, resulting in suboptimal short fill.
On that note, check out the east section. Constructors might typically put a black square at the O of CARDIO, helping to give that east region much more flexibility — with ADSLOGAN and PREALGEBRA fixed into place, there's not much wiggle room. AMICI is an odd word for an early-week puzzle, but as long as the crossings are fair, allowing most solvers a clean finish, I can give it a pass.
But AMICI crossing ESAI crossing FEIN … hmm, no bueno. I got those right because I do a ton of crosswords, but this isn't a good way to encourage newer solvers. I would have asked for a redo in that section alone and asked to smooth out WORF / WBA as well — even this Trekkie thinks it's not fair to expect people to know WORF.
Nice, novel concept, but I would have liked the grid tuned more toward early-week smoothness.