➡️In the plane of demons there are several "kingdoms" and within these there are hierarchies, the highest is the rank the greater is the power or influence they have.
➡️There are several types of demons, those of the same type are usually together in the same planes and within these there are usually different "kingdoms". Examples of types of demons: Hellborn, Lowborn (Lucifuge Rofocale), Fallen Angel (Lucifer), Abyssal, Succubus (Lilith) etc. Some are hybrids of various races.
➡️Each one has certain characteristics and tends to be better in certain areas or others, I don't know if there are realities where they join or can move to a reality that is not theirs, although I suppose so since their essence is the same or similar, just like humans and their races, in general being different doesn't mean that we can't live together or go from one place to another.
➡️Answering your question, a demon god is superior to a king, a king is superior to a commander, a commander is superior to a high ranked etc. And so on (this doesn't mean that for example a high ranked of a "kingdom" can not be superior to a commander of another, there are levels, except for those who have part of god which is an essence that in most cases puts you above a simple demon) (There could be more ranks) (There are also powerful demons not ranked that don't occupy a "state" position to be given a rank).
➡️Just because a demon is more powerful doesn't mean he has more synchronicity with you or that he will influence you more or connect better, but instead they may have more tools in their favor if he can't do something, he will send one of his servants to do it.
➡️A demon companion is a partner with who you will establish a connection of open friendship and this can continue beyond this life, it is different from a pact and less serious in certain aspects, although they can help you achieve your goals if they want to, usually any kind of offering to them is voluntary.
➡️It is best to avoid putting certain conditions to your relationship because it would be close to a pact, although they can be useful if you don't like certain things, so always ask that there must be acceptance from both parties before doing anything weird. A pact its not a thing that you can take easily, its a contract that can detroy your life if you dont give what you promised.
➡️And keep in mind that the connection can be forever, maybe in life you like to have a being around you but in the afterlife you can find a being with characteristics that you don't like, make sure that the being is ideal for you in every aspect, and if you don't want an eternal connection say it before so that it is temporary or that both of you can leave it when one of you doesn't like the relation anymore.
➡️If what you want is a partner I recommend that you ask for one that has impeccable synchronicity to avoid failures and if it is not impeccable don't accept anything, don't focus so much on the rank if you only want a partner, but if you want it to help you achieve certain goals add it to a list of priorities along with the general good synchronicity.