As you well know, every Body is different. That said, I use a nebulizer (breathing treatment) in the late morning and sometimes afternoon. This allows me to take my maintenance inhaler much later in the afternoon for the whole day. Without a work schedule (Retired), I just use the rescue puffer at other times if I feel shortness of breath during my daily routines. Or NOT 😉

Since your main inhaler is a mist (not powder) it shouldn't matter if you want to kick back for a nap or something after taking it. I just like to stay moving as much as possible, especially after my meds. I have a couple others I take near night time which probably give the most comfort for my sleep hours. Ask your Doc about Theophylline as bronchodilator to relieve some of the chest tightness.
be Well.

Actually both.
After flare-up in January I have to use rescue inhalers regularly. Also my maintenance inhaler changed to Breztri twice a day.
I use rescue at about midnight, after waking up with a tight chest and it helps me settle back to sleep. I take Breztri at 4am when I get up for work - but on the weekend I want to lie in so go back to bed.
When I got the flare up I couldn’t lay down to sleep, I had to sit up and ‘rest’ the little bit I could. After the third night of no sleep - that’s when it hit. I couldn’t seem to catch my breath, called paramedics and spent 5 days in hospital.
This originated from a chest infection that after 4 days of prednisone wasn’t abating.
There you have the whole story.
Now I get a little anxious when I feel my chest tightening up and getting short of breath. It’s been quite a big change in my daily routine.

Which inhaler are you asking about? Maintenance or rescue?
I am not a Dr or pharmacist, but I don't think you need to remain upright. After you inhale it as deep as possible into your lungs and take a few breaths you could lay down and rest.
I am usually struggling to breath when I use my rescue inhaler, so I don't think I could lay down. I need to take a three point stance and do some pursued lipped breaths. But we are all different, do what works best for you.