21 is criminally underrated. D1 and D4 can all jail into it. D4 is especially tricksy because you can enforce some mind games by mixing up advancing to pressure with 21, dash canceling into another D4, backing away to poke/zone, etc. My go-to nowadays is to toss out 1-2 more D4s after the first hits to force the opponent to sit still and respect the threat then begin mixing it up after they're petrified in fear of doing anything other than low blocking after receiving a D4.
This pressure style becomes considerably more dangerous as the set progresses. Advancing to 21 can become advancing into 212, another low poke, a grab, literally just ducking to bait a D2, a jump in, forward jump air glaive, etc. Backing away to poke/zone can become baiting a jump in, B2, glaive, F2, B1, air glaive, just backing away, fakeout into actually advancing (mainly in Jaded with vault), etc.
I've also found that despite its shitty startup time, Parry has become an integral part of my playstyle against certain opponents. It's a VERY potent way to essentially smack your opponent with a stop sign. Opponent is D1 happy when you're advancing / staggering? Dash cancel into parry after poking or during staggers. Opponent is D2 happy for your grabs? Advance like you're going to grab (walk into them for a moment while they're blocking) then parry. Opponent is stagger happy? Once you get a decent read and poke them out, either parry immediately or take a couple steps back and parry. Most people really want to poke war after being poked for some reason, or they like to immediately chase you down with their stagger string (cough Liu cough). Once you've landed 1-2 parries, opponents tend to be terrified of contesting you so your pressure becomes free game again for a while.