If you are using it for short trips and have no need to go 10 miles and back a small 2-3 HP engine is fine. I have a Honda 2hp and being air cooled it does not suffer the ravages of salt water, used regularly we use about a gallon per 3 weeks at anchor.
Weighs about 30 lbs, the integral tank holds a qt and we carry a gallon in a can if we are going further than we'd like to row,.. Anything over 3 hp is going to weigh 60lbs plus another 50 for the fuel tank. We did a 3 hour trip last week and use a qt of fuel.
Lots of electric options, but range is decidedly limited when compared to gas. When pushing a fully loaded dingy the range estimates advertised are optimistic. But for the occasional trips to shore and with a solar panel to recharge it they do the job.
Dinghy , we have a 9 1/2 Anchilles and recently replaced the plywood floor with an air floor Cut the weight in half, rides better and more comfortable. I can lift it into the car alone. We find that size allows 4 passengers and is dryer in windy weather. Hard floors add weight and in some types the floor angle is uncomfortable, but in areas where landing as rough it might be the only way.
Tow, davits, or on deck. Towing is common and with a proper floating bridle and safety line works well. But that second line will save the day at some point because when the tow line parts it does so silently. I can not recall a summer where a lost dinghy orphan was not seen.....
Davits and 'Dinghy Tow" are options. I use a Dinghy Tow and it works well . On deck works on a 30 . If you have more than a 3 hp engine you will probably tire of towing, the weight kills boat speed. And with a 60 lb plus engine to mount and un mount and the 50 lbs of gas... you'll be looking at davits/dinghy tow or at the least a hoist for the engine. Personally I would not tow a dinghy with any engine mounted, the wear on the transom, potential loss, and drag is too much when you add it all up....but lots of folks do it.
Only other thought. Use fresh gas and pay for the non ethanol high grade or marine fuel. Every time I used last years gas , well it's plain annoying and by now Debbie says I should know better. Marine engines and ethanol do not play well together.
Welcome to the group
Cheers
Thor