>>mig4ng+(OP)
Arc has native support for cosmetic improvements. Those are called Boosts and you can interactively create your owns in just a few clicks, and also add custom CSS/JS if needed.
I use this extensively to declutter/dedistract most websites I visit: Facebook, Twitter, Reddit, Medium, Gmail, YouTube, and so on. It's a real life-changer!
>>tiltow+F81
That feature wasn't big to my browsing style, Arc's way of nesting browser views suits me more, but Orion's Saved Window feature seemed clumsy to me and I'd filed my issue on Orion Tracker.