Honestly, the encounters need reworking regardless. Part of the issue with "open world" is that there is too much volatility. I can literally reach the Gith Patrol at level 2, but I may also be level 5 or 6 by then as well.
I played through the story using tabletop. Did every encounter using 5e stats as best I could and true 5e rules, with just a few homebrew. It played out pretty well with party of 6, to a certain degree. By the time I was going to the Underdark, all characters were level 6.
Here's what I discovered. Some battles are too easy. Some still nearly wiped the party. Gith Patrol, level 5 party, still almost wiped them. Spider Matriarch, only used 4 level 5s, almost wiped the party, but I made her a mage also with the ability to cast Fireball, because, you know, she's an Arachnomancer according to the story.
My point is, regardless, the encounters need tweaking depending on what they're going for. If they want you to have every fight be epic and exciting, the encounters need reworking for party of 4 once level cap is lifted.
So, regardless of what party size they choose to give us, they need to rework encounters.