Poeltl is similar to Grant. Poeltl will probably get more than Grant, but same range. Also, Grant is a RFA but I believe Poeltl is a UFA. What this can come down to though is who has cap space as much as what a player's straight worth is. Poeltl and Grant will both face this. Neither is quite good enough to get a big contract. The limited teams with actual cap space will have better options to spend on. Once you are past that, you are left with exemptions or sign and trades (and resulting hard caps).
Traditionally, bigs like Poeltl get overpaid, like Olynyk and so many others. They end up becoming bad contracts but not necessarily bad players. Once Poeltl tests the market, he will probably end up signing with SAN. Same for Grant signing with us. I don't see Poeltl getting traded, but maybe. Again, he is not quite good enough to put a contender over the top. He can help, add some bench depth, but what is a team going to give up to get that. You need to match salary and add picks.