I run Blades primarily with 5-6 players, but have also done so with lower player counts.
It works great.
As ever you need to calibrate how hard you can push your players, but I find that is more group and situation dependent, than it is player count dependent. Some groups prefer grittier, tougher experiences.
Based on my experience I would say that no player-count specific changes are required to play the game. Rules for tweaking how gritty/hard you want the game to be are included in the book†, and may be of use, but are not necessary.
†For example; tweaking the payout for scores up or down, which impacts how easily the players can recover stress.
In fact I would say it is easier to run at higher player counts than any other system I've played (Pathfinder 1, Pathfinder 2, D&D, Fate, Genesys and FFG's Star Wars).
The reason it is easier, is that the GM makes far fewer rolls and doesn't normally have 'your own turn', as 90% of NPCs only take actions in encounters as consequences to, or as interference with the PC's rolls. It enabled me to give my players a far larger percentage of my attention and brain space, and I actually enjoyed it a lot more than DMing for similarly large numbers in other systems.