Action days can be a bit hit and miss as you never know what, or indeed who, will be on track at the same time.
Combe do a fairly good job of providing specific slots for specific genres thus separating a fair bit of it out and are very hot on policing etiquette although obviously can only be done after the session.
I've been out in sessions in Mini's, kits, Porsche and track focused monsters so have seen it from all points of view. If people use their mirrors and senses it all works out ok. I've never had an issue with an action day, worst I've personally had was at a Mini specific event when somebody had cooked their brakes and had no choice but to slide up the inside of me as they had no retardation, that could happen anywhere any time and there are run off areas anywhere that is likely to happen.
I've also been one of those over committed myself, came over Avon Rise in my old 170bhp Dutton B+ to find a Westy S8 having a 'moment' with nothing left in reserve on my braking point (yes I know it's wise to get all your braking done before the crest at Avon Rise on action days now) and had no choice but to take to the grass to avoid a bang. Who's fault was that? Mine I'd say as just because I can put a car almost anywhere I like at will doesn't mean others have the same talent.
Just be respectful of the fact that there will be various levels of grip, horsepower and indeed brain power on track and you'll be fine. Think of it this way, would you put your car up the inside of an truck on a roundabout no matter how sure you were that you could get out before they cut across?
If the answer is no then you'll be fine on action days too, it's fairly easy to spot those who might be a little 'hard of understanding'.
If the answer is yes then please let me know which session you book in to so I can be in a different one
To me action days are a good place to get a bit of track time without the commitment and expense of a full track day. Almost everybody I know who has taken their car to a full track day for the first time has missed some or indeed most of it due to finding the weaknesses in their car which they would never have exposed on the road (honestly officer) so a couple of 15 minute sessions on action days are a good way to understand your car at 95% before you take it to a full on track day at 100%.
If you are a bit nervous of what / who else might be out at the same time then maybe it would be better to wait for the Kit/classic action day on the 20th June as you are only going to find people who treat their cars like you do out on circuit, also the paddock will be more interesting too
Just my opinion of course based on two decades of track days, other people will have different ones.