I'll note that Freeza was dramatically more powerful than any other Frost Demon, to a huge degree. It's not clear from the OP if I'm using Freeza's power level or if I'd be a mook Frost Demon. Imma assume it's the later because we really don't have any feats for the mook level ones to go off of.
Going off Invincible it seems like three Viltrumites are powerful enough to destroy a planet by punching it to pieces, while Freeza can do it alone even using a small fraction of his power at his weakest form. Going off of general feats I think most DBZ characters are much more damaging with their energy blasts than their muscles, we see a lot of dudes blowing up planets with a beam of Ki and no planets being shattered to gravel from a punch, and a majority of finishers are from ki blasts, few main villains ever die to physical blows. This being the case, it's possible that Viltrumites are physically stronger than Frost Demons, though I would not bet on any Viltrumite walking off a hit from a Death Ball. Consequently my initial strategy would be to train speed and do my best to never let them grapple with me while pelting them with energy blasts at range. This won't be easy as fast as they are but Freeza's not exactly slow either.
There's approx. 50 Viltrumites still alive at the time of Invincible. That may be enough to overwhelm a Frost Demon but they'd take horrific losses and they'd basically have to strip their empire of all it's manpower to pull that off. Even if it only took ten Viltrumites that could take them hundreds of years to put together, both due to numbers and their tendency to operate on ludicrous time scales. Even that presumes the Empire knows how many it needs to beat me and that it's willing to piss away like eight of their extremely dwindled numbers in order to buy enough time for the last two to get in range to wring my neck. I find it just as likely that they'd quietly decide not to invade Earth at all and hope I die of old age in a short time frame, rather than take the kind of losses it would entail.
Honestly the Viltrumites themselves, I find less threatening that all the other crap in the Invincibleverse. I'd be more worried about being erased from the timestream or trapped in a pocket dimension or some such. Viltrumites are terribly strong but don't pull all the tricky stuff that bypasses strength, and being Freeza strong, that's what I'd fear would beat me.
Consequently staying on Earth is actually probably a good idea, in order to gain allies with traits like super-intelligence who can cover my back against that sort of attack. It's also a bit of a higher-risk strategy since Earth has a significant portion of crazy going on but still, I'd find it a decent strategy. Being an official hero might also give me a chance to spar with Omniman under non-lethal circumstances, letting me get a better idea of whether or not I'm actually outclassed strength-wise, which would be a tremendous advantage compared to finding out when it's too late and a half-dozen Viltrumites pop up in front of me. Besides which Earth is my home and I'll just be happier there, even on a weird comics Earth, than random alien planet #5921.