Drake toilet water plumbing connection

My question is technical and is directed solely to the water connection at the toilet tank. I have always used bendable chrome copper tubing for connecting toilet tanks -- This Drake is my first connection to plastic, in the past all were solid Brass. Checking at my local DIY center I noticed (besides the fact that most are using flexible SS tubing) that bendable chrome tubing is available in 2 forms, a flat top version and a dome top version. I have always used the flat top version with solid Brass.

What is the specific use for each type ?? see photo

The dome top is for lavs with a 1/2" nut
The flat top is for toilets with a 7/8" nut

thank you.

Is there a preferred connection for the drake toilet - It's an ADA compliant replacement for a regular height 25 year old Kohler - the flat top chrome tubing length with bends is 9 3/4" - a 12" SS flexible is excessive and a 9" is too short?

You can get longer rigid copper supplies.

Or just let the flex connector bend a bit.

Thanks again - decided to use chrome bendable tubing now that I know which is the correct top. Since I have a tubing bender, inlet water supply was easily installed.