Mine was already in a BBB by that age too. I would move to a bed ASAP due to the climbing tbh. I think these days many people leave moving to a big bed much later than previously but that could just be my hunch.
We had a gate across the bedroom door so I could shut the gate or shut the door or both. If yours can climb a gate though I'd spend time really instilling that this (visual) barrier is a no go. Absolutely no climbing the gate, not just for safety of the stairs but so you have more trust that he is in his room where you expect him to be yk?
For us there was no change to naps or night sleep with the transition to BBB - FX you experience the same.
We didn't use any bumpers or toddler rails, I had planned to but when I read around about it there seemed no need. Instead we did a 'bed safari' which is heaps of play on and around the bed in A time, crawling on the bed around the perimeter, climbing up and down, walking around the bed etc etc, this makes a mental map of the size and shape of the bed, the sooner that map is in place the sooner they don't fall out, it's the same as adults do to stay in the bed all night. I put a couple of spare pillows and a duvet either side on the floor initially to soften his landing if he did fall out, only happened about 3 times though.
Toddler beds tend to say they go up to about age 4 I think, so maybe think ahead on it. If you buy a toddler size you only have a couple of years in it, less if your LO is tall. My boy is 4.5 and still in his toddler bed (it was a cot-bed) but we've just got a small double which will go up in a couple of weeks.
I also know someone IRL moved her toddler to a double bed when she was about 1yo with no troubles. I wouldn't have had the guts at that age but at 2.5 I don't see a problem, just look for one that is on the lower end of the scale rather than the higher end of the scale so the fall is not too far. There's also no harm in just a mattress on the floor which then moves onto a big bed later on. so many options!
