On the trail I would ride him collected with periods of relaxation mixed in. Don't want them all strung out regardless of where I am riding. I also use the same cues regardless of trail riding or show ring.
Yes.I usually change the bit for different things. Not so much to add pressure but to let him know that when he is wearing this bit its all business and when he is wearing another its ok to relax a little. But the cues do not change.
What I would do is get the horses attention by picking up the reins or whatever you do to get it and THEN ask for the stop the same way you ask when your showing. Ask with your seat and if it turns into a fight be prepared to win it. Most of the time when our horses don't respond quite as well as we think they should it's because we weren't asking in the best way. I would also let him travel relaxed with periods of collection not the other way around or your liable to get to where the work is with a tired horse.^ The thing is, even if I asked for the stop with my seat, I know that out on the trail he wouldn't bury his butt in the ground and it would turn into a fight. For him to respond like that I need his attention 100% on me, but on the trail I don't want that - I like having an independant mind out on the trail as they often see things that we don't.