In my experiences, surface coating sealers won't noticeably lessen the friction coefficient (slip resistance to you and me) when the floor is
dry. However when wet it may be a lot slippier.... BUT I wouldn't be worried about slip hazards in a domestic home. What do you do when you mop the floor? Keep everyone off it until it's dry!!
Tony, M-power is a fantastic product for a variety of uses but it is not the right choice for this. You would need to test out several things and maybe need to use more than one of them to get the right result. You're dealing with decades ( or maybe a century or more?) of soil here. I would be trying a heavy duty tile & grout cleaner, which will have a moderately high pH, I also quite often use a stripper which will be very high pH and it can often get a remarkable result. The other approach is something with phosphoric acid in it, but that would maybe be aimed more at the grout.
The cream coloured tiles probably won't ever come up like a shiny new penny, so I would pre-qualify that.
A pad will be the best agitation for the surface of the tiles, as long as they are all uniformly flat and the floor is evenly laid. As said above if there are any low spots a pad won't get into them - especially true on very small tiles, if some are not laid level the lower half of the tile won't get cleaned very well so you get a kind of clean triangle on some of them!
I would not go in as heavy as a green pad to be honest, maybe start with a white which should be enough, maximum red. Due to the age of these floors, there may be wear issues to consider. The way these tiles are made, the original top surface of them will be a lot denser and less porous than the centre. If it has worn through to the more porous material, not only will it have absorbed more soil but it will absorb the solution as you're trying to clean it. A simple wet spot test will tell you, although the other give-away is the fact that the tiles will be less shiny if worn down. OH yes and too heavy a scrubbing pad will wear yet more material off them, increasing the dullness! You can't polish that back in with a sealer so be careful.
If you've got a brush attachment on your rotary you would probably want to give it a whizz over with that too, so you can get to the places where the pad can't. If the grout is original it might be in pretty poor condition, and it might be a lime mortar grout which is pretty soft. You need to be a bit careful
Another sealing option is Aquamix "enrich n seal" which isn't a shiny surface coating but deepens and... well, enriches the appearance
When you have the time and budget, get yourself on a couple of the different hard floor courses available - it'll help you out no end
