some ideas i think of:
more forehands you can play in the rally the better probably but if they are playing balls to your backhand side from a little further away, a soft control backhand block to smother ball a bit and make them play next shot more up is good (might take more than one block). makes them move back in or be forced to reach from back. blocking down the line should get a ball you can use forehand on (be mindful if they are good at sidespin to make ball jump further away though)
and then for the forehands, think which side they give you weird balls back more often from and avoid going there except to vary, and see which side they struggle to deal with your attacks and go there a lot more often even if they are there. similarly, if you find yourself missing the crosscourt attack but nailing the straight shot (or the other way around), just stick with whats working more and finish stronger.
dont use as much energy on the in between shots since they arent going to counter that often but make sure you are consistent and purposeful with those shots to set up the finishes. ive accepted i have to respect the weirdness of the ball more and figure out the right way to approach the rally vs these types of players, but then when u lock in you can blast it. a lot of times it comes down to the ball being a little closer/farther than expected causing errors, or playing too hard and the spin causing errors.
try serving mostly low double bounce dead balls to attack returns right away while they are close. dont give them so much spin on longer serves to use against u if you arent winning points or setting up your shots that way. then once they are staying closer for shorter serves, you have more freedom to use other tactics (prob still more flat and fast long serves then spin though). and can mix in some short underspin or spinnier serves so they make mistakes on those too
i think its nice to kinda narrow down your serve and rally tactics vs this type of player so you arent overwhelmed with options/scenarios, as they are going to try to use variety and randomness to their advantage. similarly, i think these types of players all have their own things they are good and not so good at, so its about figuring out the particular allround/defender's game out a bit more and what you can exploit with your attacks