Personally I would forget 20 inch. I like... Echo 2511t top handle Echo 2511wes rear handle Battery saw Brushcutter I have all. The 2511t is my top choice. Even though it's a short bar. Used to be THE lightest saw maybe still is. I use it for exactly what you are doing and even bigger trees. You can't believe how light! Battery saw needs multiple batteries, yes, but I love mine. I have 16 inch on. The brushcutter would maybe be the champ but about 3 inches is limit for mine for extended use. This from someone with back issues.
There also is a 192, 193 of the same style for a lots less. Maybe even find NOS of the 193. The 194 replaced the 193. Both top and rear handles. They are a lot easier on the pocket book at almost half the price of a 201. I picked up this 192 rear handle in December. Friend who works on saws has it to get it working 192 & 201 7.3lbs vs. 8.6 for the 201. Powerhead weight
I love my 2511 P. Kevin ported it and I run the echo 3/8 lp 0.43 narrow kerf set up. Cuts smooth and fast. I had a T ported by someone else. Sold that when the P came out.
I had an Echo cs-400 for a few years. Loved how smooth it was. It had a 16" bar on it. That saw would have been perfect for what I'm getting into ! I think they made a lil 18" bar for it. Wonder if they make a 20" for that chain size and mount. Hmmm. Only using the last 2-4 inches of the bar anyway lol .