Unfortunately, I can't answer those questions. All I know is that between the tile store where I'm getting my tile and my tile installer we're doing a number of changes to the tile I'm purchasing including making bullnose out of some of it and cutting and honing the edges on another tile (I want 6x24 but it's not available so we're going to have 12x24s cut in half and honed). If you're working with a tile store and an installer I would think they'd be able to have the same thing done for you. If this is a DIY project that could be more complicated, but perhaps you could talk to a local tile store and ask them if they know a place that would do it for you. It does add some cost. I'm not sure about the bullnose, but I know both are less expensive than buying a fancier trim piece. For the other tile that we're having cut down, the cost adds about $2 per tile (but keep in mind those are HUGE tiles).

Rather than focus on the wall of windows you might first paint the walls a mid-tone or darker which will do wonders at warming up the room. You may not then need to dress the windows at all. You have very valid reasons for leaving them uncovered. Window coverings for that expanse of windows will be very costly and there are many other ways of warming up the room. If you are interested in having plants to soften the space you might consider a couple of Dieffenbachia as they are fairly inexpensive when small and grow quite quickly. Of course there are warnings about the toxicity but I've never had kids or pets eat them and I have read that warning is over-rated. I've had one grow to over 8' tall and seen them much taller than that. They actually do better in lower light situations and mine did well in a north-east window. Whatever plant you choose you could put it on a pedestal when small for greater impact. I'm not a fan of accent walls so wouldn't advise painting the fireplace wall a different color. Too often accent walls don't work as intended for interest and I think there is enough going on in this large room so that keeping all walls the same color would be best.

This long and narrow bathroom reminds me of the one I grew up with in Brooklyn. It had the same problems you are facing. I highly doubt there is a radiator in this bathroom. The OP can comment if it exists or not. The large diameter steam pipe in the corner is a typical set up for bathrooms in old buildings. There is probably one thermostat controlling the heat for the entire building. The apartment above does not get to set its own temperature. How warm you apartment is in the winter is determined by what floor you live on. I agree if this is the only bathroom then it should to have a tub. I am not sure if re-configuring the tub is going to lower the resale value on a $1M+ coop in NYC. Putting up the wall between the tub and the sink makes the shower more functional. But it will make the bathroom look smaller and block some of the light from the window. I still think if you are going to move the tub the something like this one at Home Depot could work. It is 6 inches shorter than a normal tub. You will need 54 inches from stud to stud which may be possible once the plaster and lathe are removed from the walls. You could install the tub 8-10 inches away from the window wall. A shelf could be built between the tub and the wall and covered with tile. That becomes a place to hold your shampoo bottles and soap dish. Most of the steam pipe would still be exposed and will keep the bathroom warm even with the shower curtain closed. The shower head and controls stay on the same wall. This will open the space to put in a 36 - 48 in vanity with a granite counter top and a wider medicine cabinets and better lighting. That will give you ample storage space. Something that was not an issue when this bathroom was laid out 100 years ago. Have you asked any of your neighbors if they have remodeled their bathrooms? It would be helpful to get ideas and see how they dealt with these challenges.

Elunia is spot on...he started with the full tiles at the end and worked in. I would have capped the pony wall with a piece of white quartz - clean and simple. I think that once you are using the shower and the bathroom is done you won't notice it as much. Plus it looks as though the grout still needs to be cleaned up and wiped off - I bet the grout lines there will look better. BTW I like your hex floor!