Are you referring to things like right after Manufacturing Collective you get 3 research choices. One for +10% production, One for +10% research, and another one that reduces costs by 10% (I think).

If I'm following your train of logic and am right about what you are referring to then you research one of these 3 and the next tech in the tree opens up. However the 2 you did not research remain there. From your phrasing it sounds like you think you can no research the other two without losing the one you had before. But these are cumulative options. You can have  all 3 if you choose to invest the research time.

If I have miss understood you then apologies but you are extremely vague about what you are referring to.

Yes, you can research as many specializations as you can find. I would not recommend it though.

I've found that there are many techs past specializations that are worth researching. Focusing on nabbing more specializations than you need can be a distraction. For instance, the tech needed to enable tourism is not a specialization. Tourism is a new source of income (that you don't start the game with) that does not require you to divert production to get. Bigger ships are very useful. Planet improvements to get more population, and planets improvements to boost morale is useful. Many planet improvements can be placed multiple times (so you get the benefit multiple times), but bonuses from specializations is applied only once.

Do you get what I'm trying to say?

I haven't seen any real mechanically difference between normal techs and specializations. Aside from the multiple choice part, the only difference that I've seen is in the way they have been used thus far. The specializations might offer things like smaller weapons, cheaper weapons, or better weapons (offered in percent improvements). For instance, a specialization might reduce the size of all missile weapons by 20%. Normal techs tend to offer new things instead of improvements to existing things. For instance, they might unlock stingers or harpoon missiles.

I suspect that if you wanted to mod things, you could make the specializations unlock different ship parts and planet improvements, and make the normal techs give bonuses only. I'm not a modder, but I think you could make a line of techs that combine all weapon techs into one branch. With that branch, you might be researching weapon techs in general, and for each specialization, you choose if you want lasers, railguns, or missiles. Each of the normal techs might simply be percent increases to firepower or something.

I noticed them of course, and have been playing with them so far without understanding exactly how they differ from regular techs, so I asked.