Rolland if you can figure out how to get by with nose pillows, you will be better off. I also started with stuffy nose and mouth opening. I thought I would always have to use a full-face, but i'm happily on nasal pillows.
If you nose is stuffy, things get complicated. I now use a saline nasal rinse (discussed often on this forum) and my doctor gave me an RX for a nasal decongestant-nasonex. Do not use over the counter spray. It makes it worse.
Open mouth-I hated the chin straps, too cumbersome and didn't work well for me. I now use a pad between chin and chest that works great. I have improvised the pad. You can roll a couple of wash cloths to the proper diameter. I now am using one of those "cool-band" things that keesp your head cool. My wife removed the contents and filled it with uncooked rice. the ends can be tied around the neck to keep it in place.
OK, so if you can get your nose working and something to keep your mouth closed, you should be able to use a nice nasal pillow rig successfully.
I’ve used OTC nasal sprays many years ago. Read the instructions, (yes that is new for a guy to do), which said not to use it more than 3 days. So I would sleep well for three nights, and then spend two nights suffering from congestion. Then start using it again. One time I wondered what would happen if I used it more than 3 days. So I tried it. Got away with it on day 4 and 5. Day 6 was miserable x10. Not only was my head congested when I laid down, it was congested while I was up all the next day and all the next night. Over the years I slowly stopped using it. Now I just use sudafed, maybe 2 times per week. One funny thing though. I liked working on some surrounding farms, usually working for 3-4 weeks a summer. My allergies killed me during that time. A couple of years ago I purchased a farm and now my allergies are maybe a 1/4th of what they were just 5 years ago. Don’t know if it is age that reduced my allergies or the fact that I am around the allergens 24/7. Either way it is manageable now. I would have been disappointed if I had to give up the farm. I love the lifestyle change.