Honestly don’t worry about your age at all - you will be fine and will make awesome friends
I was 35 when I went, average age on our trip would have been around 28 I’d say
We had a few young ones but also a few older than me - one guy was 39 and having the time of his life!!!
Ohh I haven’t heard of Flash pack before - do they have similar trips?
I have done contiki before through Europe.
Both companies run pretty much the same tours but I liked that with Top deck we seemed to have more free time to do your own thing.
There are optional activities you can sign up for but there is no pressure to do them. (you sign up for them on the bus couple of days before arriving in each place) tour guide usually has more info too.
Budget to do them even if you aren’t too sure about them - at least you know you have the $$ for them.
I found Contiki had a BIG drinking environment…hehe maybe times have changed since I did that tour, plus I’m older now.
There was no pressure to go out partying every night when i did Top Deck & no judgement if you didn’t do out.
Hope that helps…anything else you wanna know about, ask away