No but they should have some sort of element that ties them together. Like same filament bulbs, or same glass droplets or same colour.

They look great in that photo, Northstar! Works beautifully. Will be fine over your bench. Didn't realise how large your p really space will be. Wow! No, if you replace pendants that have staggered drops, the fittings are completely removed and new pendant fittings are installed in their place. The electrician just shortens the drops without cutting them & the extra lenth is hidden away in ceiling.

Though I don't know for certain, I think the cotton/linen shades are removable. I wasn't able to determine this by my searches. This could easily be confirmed by making an enquiry to supplier before purchase. Alternatively, a handmade one could be made removable by making shade slightly larger than frame and making ties.

No down lights in bedrooms. A central pendant fitting with LED bulb, or a central fan with light. Then bedside table lamps. lounge and living spaces- depends on the size of the rooms. In my opinion there is nothing worse than a runway of lights in the ceiling. A central pendant, or two matching pendants, if a long room, always looks the best, in an older home. You could then bring in floor light stands, that will also add to the character of the space. Or a trio of lights in the corner of the room, if space is available. An abundance of down lights, in my opinion, would not look the best. Remember for energy efficiency use LED bulbs.