I would answer the subpoena by showing up at the committee, make an opening statement condemning the entire charade, then plead the 5th to every question after that....
Basically make a mockery of the entire situation, they can’t force him to testify, they might be able to punish him for ignoring their subpoena....
They'd likely say that by having an opening statement you were waiving your 5th ammendment rights and actually testifying. Then arrest you for contempt when you tried to actually use it.
Go there, say nothing.
Say “my lawyer instructed me to say that you are all a bunch of no good lying communists, who are hell bent on destroying thsepblc of ours, and he told me to plead the fifth since you don’t give a crap about actual evidence that proves that I’m innocent. Any further questions?”
I would answer it by having Biden's brother, accompanied by a couple of my associates, sitting in the corner of the courtroom during my testimony. Afterwards, we'd all go out for a nice ice cream.