Tips for radiators

Good day,

we are renovating a house from the late 60s, which still has the original radiators. Foremost: The floors are partly very high-quality and beautiful, and the story construction/room height does not allow for the subsequent installation of underfloor heating. Therefore, we will stick with radiators. My questions:

1) Is the efficiency level of newer radiators significantly higher so that a replacement is advisable? In the living room, for example, we would like to replace them for aesthetic reasons, but in some basement rooms the old look does not bother us.

2) If the old radiators still look good "from the outside" (e.g., no rusty spots), are they still good?

3) If we replace (possibly individual) radiators: I read in the BAFA criteria that only "low-temperature radiators/radiator strips in any construction type" are eligible for funding. The heating system will probably be a hybrid system (gas condensing boiler - air-water heat pump with photovoltaics). What do I need to consider if we would like to claim funding also for the radiators? Can I create problems for myself by combining things that do not fit together? I imagine this is particularly relevant for December-January, when the gas heating runs stronger and possibly the flow temperature is higher?

4) More from an aesthetic point of view: We have several wide/deep low radiators. For the one in the hallway, we would like to install a wooden bench above it (with spacing and possibly holes) into the hallway window. What should we consider?

5) Above the radiator in the living room (see attached photo) there is currently a granite slab as a shelf. However, this can slip and I do not find this a very "nice" solution overall. I would be very grateful for suggestions and ideas here! We have two small children, many visitors, and hopefully numerous grandchildren in the future, so safety is important.

5) Behind several of the old radiators there is something like aluminum foil on the wall, which I assume is to reflect the heat more strongly into the room. Are there "nicer" sensible solutions that can fulfill the same purpose?

You can tell that I do not have much knowledge yet. Therefore, I would be sincerely grateful for advice, suggestions, tips.

Best regards,
Träumerle

the story construction/room height does not allow for the subsequent installation of underfloor heating.

Is that really the case? At that time, floating screed with a build-up height of 70-80mm was often already used. That is more than enough (insulation, e.g., on the basement ceiling).

Regarding the radiators. The old beauties were designed for boiling water, modern radiators for a significantly lower flow temperature. Even a heat pump is sufficient for that.
Basically, the old radiators are made to last forever and will continue to do their job.

What fits you as well depends mainly on the heating load of the building and your further renovation measures. Do you have an energy consultant on board? There are also substantial subsidies through the KfW – including for the screed and floor coverings.
Radiators come in all shapes and variations; maybe the one in front of the window can be replaced with one mounted quite close to the wall – vertically instead of horizontally as before.

Thank you for the response!
Yes, we have already consulted an energy advisor and a heating engineer. That is how we came up with the idea of the hybrid heating system. The heating load of the building has not yet been finally determined, in principle the house is very well insulated upwards, but rather insufficiently insulated outwards, a more detailed assessment is still pending.
I would also prefer a tall, smooth radiator on the right wall. But how do you run the pipes there (without damaging the parquet)?

But how do you run the cables there then (without damaging the parquet)?

Oh, so the connection is currently on the left. Then basically like in a cable duct along the floor. Or you come from the basement with a new cable up the wall.