Conditional formatting on CODE Server is laggy

I recently was looking for a self-hosted alternative to Google Sheets and found Collabora Online.
So I installed a local Server (i5-3320m) with Ubuntu, Nextcloud and Collabora Online. Everything works so far.

I made a new Spreadsheet and started to develop my table.
The table should have a bigger area (100-1000 cells) with conditional formatting.
The background of the cells should change dependent on the entry with around 10 different rules.

There i find limitations.
The menu for conditional formatting is laggy, scrolling and selecting conditions does not work reliably.
In the dialog I can generate new Styles for the conditions but I can not edit existing Styles.

The cpu usage on the server and the laptop is low (<20%).
The behaviour is browser independent (Chrome, Firefox and Brave tested).
The behaviour can be reproduced at webo hosting, a parter of Collabora Online.
The behaviour can be reproduced with another laptop (i7-7500U).
The behaviour on a local Libreoffie is much smoother (or usable at all) and I can modify existing Styles.

Does this behaviour change if i upgrade to a Collabora Business Account? I do not have a clear understanding of the functional differences between my self hosted CODE Server and a Collabora Business Server.
My workaround so far is to use a local Libreoffice and edit the document offline but i would prefer to fully work with the document online.

Any suggestions? It is my first self-hosted IT project and I am not sure if I miss something obvious.