It depends on what playstyle you’re comfortable with. Me, I wouldn’t recommend reloading too much since it can get frustrating if you repeatedly fail anyway and with stat-gains tending to even out as you level up. I can see how people would reload a lot though, especially in the early game, to make sure they’ve got good mercs.
Yeah, it seems a bit random when you can and can’t edit. I think it’s either related to how much time has passed or whether you’ve logged out since then.
Interesting note about fighting near cities, by the way. A town expends resources to create militia, resources that are recouped for any that survive the battle. So using the militia too much can result in the town weakening over time and less goods becoming available. It’s still a good strategy when you’re not confident that you can take an enemy, but there’s definitely advantages to taking them on yourself (if you win ;) ).