Cut it, I'd do a 2-2-1-1-1-1 taper with half a bar to a full bar when you finally have no more sub. You may "have" to use because maybe the day you have no more suboxone is a really super mega important day and your whole life depends on it, but you can't. Period. The fact that you're addressing heroin so casually and thinking getting off is going to be as easy as 1 sub strip and some xannys isn't realistic. This is your one get out of jail ALMOST free card. Take it, get through this, and never look back.
at worst, mild flu symptoms, maybe cravings, nothing too bad if you've only used heroin for 3 weeks.
2-2-1-1-1-1 suboxone
.2 clonidine in the morning/at night, maybe mid day if needed. I'd save it for the last two days of suboxone and the 2 days after.
Kratom? Idk the strength of capsules. I'd take 1-4 a day, no more, titrate up when your sub goes down. At 2mg sub, don't be taking as much, when you're at 1mg sub, take a few more. When you're off, take a little tiny bit more, don't overdo it and come back 3-4 weeks later asking how to withdrawal from Kratom as well.