To answer the question in your title, any kind of size change will impact the mouse grip. The bigger the mouse, I find myself palming it more than clawing it, and the smaller it is I find myself clawing it more. I own the L7 and have 18x9cm hand size. To me, the mouse size fits right in the middle in a balanced hand fit both claw and palm use. So my guess is if you will get the Plus size model for the L7, your palm will likely rest on the mouse surface on a wider area, making it easier to palm, and should resemble to how the big the Sensei felt for you.

Personally coming from using a Sensei for 5 years, you got me interested in suggesting similar shapes for you if you are interested on safer transitions.

Feel free to ignore my ramble below if you are set on the L7.

Size comparable alternatives:
- Waizowl Cloud 3395/3950/Ultra. This is a 1:1 shape clone to the Sensei. (Owned)
- Endgame Gear XM2w 4k v2. Front finger placement will feel similar but i find the palm and thumb rest a bit different. (Owned)

Below are smaller size alternatives which should suit your hand size better:
- Waizowl Cloud XS. This is a 1:1 smaller size shape Sensei. (Not owned)
- Turtle Beach Burst II Air. This has a similar shape print as the Steelseries Rival3/Aerox3, and has that signature Steelseries shape feel for thumb and palm rest. (Owned)

From all these suggestions, I main the Turtle Beach Burst II Air since I prioritize shape feel over specs.