Hi
The arrival of sows in a boars-only place will inevitably cause a big stir. Guinea pigs have a much finer nose and will perceive the sow pheromones.
If you can, keep any new sows in a different room; otherwise at a distance or on a different level (boars higher than sows because of the way pheromones travel) or with a big opaque divider higher and larger than the cage to prevent strong sow pheromones when they come into season from setting off your boys and potentially cause a fall-out if there are any underlying issues between them - it can happen even in adult pairs.
Chapter 3 in our Boar guide deals with all the dos and don'ts around boars; inclusing the introduction of sows into a room; the link also contains a chapter on neutered boars and what neutering does and does not (it mainly 'does not' in guinea pig boars):
A Comprehensive Guide to Guinea Pig Boars
Boars growing up around sows or are introduced into a sow/mixed gender room while still sub-teenage produce a calming compound that makes a huge difference. A very strong season can still mean a short term divider in the boar cage and a re-intro on neutral ground once tempers have settled down, but it doesn't usually lead to big fights and fall-outs.
A single boar can live next to sows with interaction through the bars (he has nobody to fight and fall out with) as long as he cannot climb out, jump over or wiggle though any bars or grids. A traditional cage is better or you will otherwise need to cable-tie any grids we well as create a lid on the boar side otherwise in order to prevent any accidents with full boars or neutered boars that have not sat out their full 6 weeks post-neutering op wait. Keep in mind that it is usually the pheromones of a sow coming into her season that trigger the full athletic abilities and determination of a boar - and they are truly impressive!