You can find a list of compatible handguards on the manufacturer's page here: https://www.adamsarms.net/info-media/faq?SID=6e48c73145837d4285420f5e50f0680f#qa1
Unfortunately you cannot modify a bolt to work with a left hand charging or ejection system and we highly recommend against it. Any modifications would render the bolt carrier group potentially dangerous. Most side charging upper receivers require their own very specific side charging bolt carrier group. You need to verify what bolt carrier group functions specifically with the upper receiver you have.
I'd go with quad rails, you'll need the height. Also, no you can't modify an existing bolt to eject left handed. The bolt carrier keyway is cut for right ejection only as well as the extractor in the bolt is cut for right ejection only too. You need a special "Lefty" bolt and I've no idea where'd you'd get one.