I think he's going to play very well against the Niners.
As good as their secondary has been thus far this season (impressive 57% completion percentage against), the Rams have a group of pass catchers who are going to get mismatches on just about every down. So purely from the perspective of WRs and TEs of the Rams against SF secondary I expect them to double Quick and try to eliminate him but it's not gonna work as Davis gets through his reads and has shown a proficiency for spreading the ball around very well.
What that means is that it comes down to pressure in this game, particularly on third downs which is where Davis leads the league in QB rating. Looking at the Niners' sack totals they aren't much better than us tbh, with only 5. They do get some good pressure, but their strength is their disciplined zone play in the secondary, their quality LBs being able to rush or drop very well on passing downs, and ability to get off the field.
Personally I believe that Quick, Britt, Cook, Kendricks, and Bailey are more than enough to allow this kid to keep the chains moving. Get ready for another big game from the kid, IMO.