In the new design there is a border around the viewport. Is it possible to remove it somewhere in settings? If no, please add such setting.

If window has many tabs, then not active tabs are smaller then active tab. And when you change active tab to another, old tab becomes small, and new active tab becomes wide.
Today I upgraded opera, and it became so that when I click on a tab, it looks like it instantly switches to drag and drop mode so if old tab is placed somewhere on the left from new active tab, then because of changing sizes of tabs, the active tab moves a few tabs to the right.
Steps to reproduce:

1. Open 200 tabs
2. Select the most left tab
3. Then click on the tab to the right
   Expected behavior: the last clicked tab did not change position relative to other tabs
   Actual behavior: the last clicked tab changed position relative to other tabs and moved several tabs to the right (depends of small tabs size)
   I didn't upgrade Opera for more than 30 days, and in previous version there was no such problem. This is reproduced and with tabs scrolling enabled and with tab scrolling disabled.
   Version of Opera: 96.0.4693.31
   Version of Windows: Windows 10 Home 21H2 build 19044.2130

@jessbaltrusch I just returned to version 99. But history got broken after it (maybe should to clear all history to get it work again).

In the new design there is a border around the viewport. Is it possible to remove it somewhere in settings? If no, please add such setting.

In the new design tabs have big top and bottom paddings/margins without no purpose, which just waste space on the screen and make height of viewport smaller compared to previous design. Is it possible to remove theese paddings/margins in settings? If no, please add such setting.

I just had a strange problem, that Opera was stuck for a few minutes (I couldn't click anything in Opera, nor tabs, nor open menu), and during that time it was slowly eating more and more memory up to 19 GB. After it Opera unfrozen, and memory consuption started to slowly decrease. At that time I opened Opera's Task Manager, and inside it there was no process with very big memory footprint, it looked like always, when it consumes around 7-9 GB, what is normal for me.

Also recently, such freezes (but short) and also slowdowns happen often (especially when opera is opened in two windows), which was not the case in previous versions. Current version is 97.0.4719.63.

If window has many tabs, then not active tabs are smaller then active tab. And when you change active tab to another, old tab becomes small, and new active tab becomes wide.
Today I upgraded opera, and it became so that when I click on a tab, it looks like it instantly switches to drag and drop mode so if old tab is placed somewhere on the left from new active tab, then because of changing sizes of tabs, the active tab moves a few tabs to the right.
Steps to reproduce:

1. Open 200 tabs
2. Select the most left tab
3. Then click on the tab to the right
   Expected behavior: the last clicked tab did not change position relative to other tabs
   Actual behavior: the last clicked tab changed position relative to other tabs and moved several tabs to the right (depends of small tabs size)
   I didn't upgrade Opera for more than 30 days, and in previous version there was no such problem. This is reproduced and with tabs scrolling enabled and with tab scrolling disabled.
   Version of Opera: 96.0.4693.31
   Version of Windows: Windows 10 Home 21H2 build 19044.2130