It is all about serve and receive lol. First thing is knowing how to loop the super wide FH corner serve and be able to come back to rally even if it gets blocked to the BH, if you can't do that the opponent can simply serve pendulum wide to your FH and then redirect to your deep BH and you are toast.
Second thing is how to loop the straight line deep BH serve which is way worse than the righty version because there is less time to react. Your BH needs to be strong enough to loop all the 7 types of spin for the deep fast serves.
If you don't loop these 2 variants, the opponent will get the 1st attack and you are toast too lol.
Third thing that is super annoying is short FH receive. It is so easy to serve all kinds of spin to the short FH stably so you better know how to use FH to deal with all kinds of serves there (7 types of spin again). Especially bad is the hook serve to the short FH, it is a nightmare to receive.
Fourth you need the footwork to be able to handle all 3 spots competently.
On looping, the big problem is being able to FH loop down the line, otherwise they are always waiting for you on the BH corner to block you to the deep BH and it is again really annoying to deal with.
The other thing is with explosive footwork to the wide FH, this will always be a really difficult ball. Coz the lefties all have sidespin BHs which go diagonal to your extreme wide FH. If your footwork sucks then you won't even be able to reach the ball let alone counterattack.