I don't think A&M should/would be using the transfer portal to pick up "free agents" too often. Maybe you'd use the portal to get a grad transfer QB if you have a need due to injury/declaring early/whatever, but hopefully Jimbo has a decent depth chart and plans for those kind of situations. I can't think of a non-qb that went to a P5 from a non-juco that made a significant impact. I'm sure there are some, but that seems to be the exception....
Also, from my limited observations, it seems like most of the players going in to the transfer portal are doing so to get more playing time, and are likely going from a P5 school to a G5 school, or G5 to FCS, etc. Sure, occasionally there will be a late bloomer at a small school that is looking to up his competition level, but that is pretty rare.
The transfer portal hasn't really changed much--it has just made it more obvious and transparent when a player is looking to transfer.