I think there are 2 aspects to info evenings - one is finding out about adoption and the process in general, and the other is finding the LA/agency you want to work with if you go ahead.
The general info should be fairly standard, so you don't need to go to as many as possible until you are ready to make a decision.
When you are reaching the point of signing up you are looking far more at the specifics of the organisation you choose to go with - how does their process work, what children are they typically looking to place, what post-adoption support do they provide - those sorts of questions. Then it would make sense to look around at which agencies work in your area and think about how many fit your criteria and are worth contacting.
For example, LAs will usually try to place the children they have responsibility for with families they have recruited, because it is cheaper for them. Some LAs have joined to form a consortium and all the 'consortium' families are considered for all the 'consortium' children. Therefore, to generalise, agencies will be looking for families for 'hard to place' children, because the ones that are easier to match will have been placed in-house by the LA.
However, a 'hard to place' child might be perfect for your family. For example, 'older children' are considered hard to place. But I know several adoptive parents who wanted to adopt a school age child, partly because they were single and needed to be able to go back to work without childcare being an overwhelming cost, and partly because once a child is in school you have a far better sense of their needs.
For other people experiencing the 'baby' years is important.
I read about one adoptive family that had adopted children with life-limiting conditions several times. Each child died, was mourned, and then they adopted again, they wanted every child to be loved and part of a family, and were emotionally resilient enough to be able to take children into their lives knowing that they would eventually lose them.
But for now I wouldn't worry about that too much (although getting some experience of working/volunteering with children with special needs of various sorts would be a good idea). Just go to a couple of info evenings, read a bit, carry on thinking about whether you want children to be part of your life, and if so, whether that is by being a parent.