nor me, but in similar sized rooms, I just checked, I have rads of nominal output just over 2kW. A TRV prevents the room getting overheated. IIRC I upgraded them from singles to doubles.
Housebuilders tend to undersize rads because they use a calculator based on optimistic assumptions. I used to work away a lot and in the days before programmable stats, the original rads took a long time to bring the house up to temperature, and were inadequate in really cold weather. The benefit to the builder is that it cuts their costs.
For comparison, using a corrugated flat steel radiator, it's only 1200mm x 600mm (double), which is nothing out of the ordinary in a reasonable-sized bedroom.
Looking at column rads, it seems that a 4-column rad of roughly similar size has similar output, though it will stick out from the wall more. But the cast-iron column rads I am used to were about a metre tall.
If you mean a vertical column rad, it will be pretty big though IMO tall radiators are better for heating ceilings. A low-wide radiator spreads the heat more evenly through the room.
Column radiators are very heavy.
I would probably put it on the long external wall. Near the window would limit your choice of curtains.
Opinions differ, but I find column radiators rather intrusive.