No problem with it. If you have relays on, scrap them, and use the space for something else (yes, it's only 20 decks, but hey, every little helps).

When freezing, are Artifact planets the best to have, or research?

I don't mind having them on. It generates energy when I need it. and the increase to my income would be minimal.

It's best for artifact. Artifact is exponential. The more artifact you get, the more purgers, which means the more purgers. A side of effect of this is more ship power ups, giving you more hull, defense, attack/energy (depends what you put your RP in, because defense and research are just ludacris options for using RP) research, cargo, and deck space.

However, I don't completely slow rank. Or at least, I won't. Once I get my planet slots full, I will auto rank until I have enough slots open (which I am currently getting close to this from my freeze ranking... I do have 10 energy/rank with relays and ions off, but I want to have 12/rank with ions on for auto ranking)

Given this will take me quite a while, as I just did a 301 planet scan run, and I found 5-6 planets worth taking, and with that, it would take me two more scan runs until I need to fast rank, which is at least another 2-4 months, depending on luck.