I would say don’t view lead walking as a punishment for you and be looking for the first opportunity to get them off-lead. If you don’t enjoy lead walking, your dog won’t enjoy either. That’s when you get people who will constantly walk their dogs off lead, that have no control but the dog and owner are less miserable (at the expense of everyone else).
Off-lead in a busy area only when you have decent control and can recall them from dogs on leads, walkers, runners, cyclists, children, cats... We walk ours off lead in a country park that is usually quite busy and will have all of the above going on. If a dog is on a lead, we tell her to leave it. If she isn’t listening to us that day (she is well trained but she has the odd rebellious day), she goes on her lead until we’ve passed. For cyclists and runners, we will recall her and get her to sit on the side of the path until the cyclist/runner has passed. I think it’s always better that the cyclist/runner sees that your dog is out of the way and under control, they know they aren’t going to be chased then. We started with recall at training, so a controlled environment with no distractions. We built up to off-lead in quiet areas such as fields and woods. Then up to busy areas with lots of distractions. We also recalled with balls, treats and praise rather than just relying on treats all the time. We inadvertently created a game where we would stand in a field and call recall her to each of us in turn. It’s still her favourite game, just running between us. She was probably 18 months before she continuously went off-lead at the country park. We’ll still stick her back on her lead if we’re passing a particularly stinky ditch because as good as she is, she has selective deafness when it comes to stinky ditches.
We started by walking our dog around the back garden on the lead. We also live on a busy road so she’s not allowed out of the front without her lead on, nor is she allowed to jump down from the car without her lead (and being told ok). So for us, our dog has associated the lead with being able to go somewhere fun, even if she’d prefer to be off-lead. We had a battle of wills for a while getting her to walk without pulling and I think that’s when most people cave because the dog will walk relatively close to them. We just just had to be more stubborn than her and now she walks beautifully on-lead and off-lead.
For when both dogs are on-lead, you allow a few seconds to sniff each other and say hello. If a dog is on a lead and has a harness that is yellow or red with wording that says anxious, nervous, aggressive, blind do not let your dog approach. That dog needs it’s space.
Sadly, not all owners of anxious or reactive dogs use the harnesses. So you need to watch for body language too. On-lead and off-lead. Far too many owners of reactive dogs will allow their dog to walk off lead, growling at passing dogs. You need to watch your dog as well as the other dog, separate the dogs if the body language is too excited or too apprehensive. You can do that by walking on. If the other dog is off-lead and following you, tell the owner to get their dog back.
If you’re in an area that requests leads on, say a nature reserve for example. Keep the lead on. This is usually to protect the ecology of the area that will be disturbed by a dog barrelling through. Or it’s because it’s a busy area and you need to respect other users too. You can still have some lovely walks with a dog on their lead.
Personal pet peeve - if a dog is training off-lead, don’t approach it on or off lead. We were in a country park in a little clearing off the path. It was busy and we knew people would be walking past but wanted to train with her. We hadn’t taken up the whole of the clearing so people could still use the space and take a shortcut through without disturbing us. We were training our dog and this was pretty obvious as she was sitting, looking at us and waiting for instruction which we were saying clealry. A woman allowed her off-lead dog to run off with our dogs retrieve article and another walked up to us with her on-lead dog and encouraged her dog to play with ours, even though hers was still on the lead. Had our dog been interested in playing, and she is really playful, we’d have let her play but she wanted to retrieve her articles. Unfortunately doing training with your dog on a walk is odd, so people investigate and generally cause a distraction.
From a lead point of view - you don’t want a retractable lead as you don’t have any control of your dog on one of those. People who let their dogs on retractable leads go up to an on-lead dog are the worse. In their eyes they think they’re being polite because their dog is on the lead but it’s still approaching a potentially reactive dog. Or a person who doesn’t like dogs.