Caufield's frame is not going to allow him to add much weight, he's probably going to be similar to DeBrincat, who is a top scorer, but otherwise pretty much a cipher. The problem is these are guys you want off the ice with a lead, and who often disappear in the playoffs when the windows get tighter and there's a lot more contact. There's a reason he dropped to #15, and it's not because teams doubt his scoring, but the object isn't to score the most goals but win the Cup.
Top 9 teams in goal scoring: 6 exited in the first round, San Jose was saved by the refs, Chicago #8 and Florida #9 didn't make the playoffs. Flyers were 12th in 2017-18, 18th last year, I expect with AV and the addition of Hayes, Frost and eventually Farabee, Ratclifee, Rubtsov, etc., they'll be consistently in the top ten in goals scored without adding a "scorer."
Brink has more risk than Caufield, but he can probably fill out to 5'8 175-180 (stouter than Caufield), a size where you find a lot more small players succeeding in the NHL and some even capable of playing two way hockey.