Wilson is a banger...did you watch the Final Four last year? She was relentless on the glass and is not afraid to get physical like she was earlier in her career. I'm not expecting her to stop Fowles or Griner, but she's a much better option to counteract them than what they have right now. Her game reminds me so much of Tina Charles in that she can has very good length and athleticism, can hit the face up jumper, has good basketball IQ and can finish inside. Similar build and potential IMO. Plus A'ja is a workhorse and seems to have the drive and motivation to be great.
I do not think she is going to dominate, but she has all the makings to be an outstanding PF for years to come and be a player San Antonio can build around. They need a SF too, but the biggest issue is they do not have a viable post threat or defensive presence to stop opposing bigs. They need someone who can battle on the glass, block shots, and provide an inside presence to open things up for McBride and Plum/Jefferson.
If they take a SF, Deshields in theory is a better option than Williams since she has more size and better ability to create her own shot, but she has big red flags around her considering her marginal success collegiately and she's never shown great basketball IQ or shot selection, both of which can be death warrants in the W. I wouldn't want Deshields taking 10-15 shots per game over McBride or Jefferson.
Williams is a great facilitator and finisher, but San Antonio already has a slew of good passing guards...they need a front court player who can put the ball in the hole, and Wilson fits that bill.