Looking for experiences with window sun protection glass

The following questions:

1. Is the heat gain significantly reduced?
2. Is the light gain significantly decreased or is that negligible?

That cannot be answered generally, because there is solar control glass with a wide range of heat protection and sun protection. It depends on your requirements. You have to "play" with the values and choose the appropriate glass. You also change the facade if you take a strongly reflective solar control glass. Then you can incorporate color effects through the different coatings. Do you want that? Also consider that the solar control glass works even when there is no sun.
You should have the different panes offered to you, have the values explained, and request samples.

So, my pending response: We now have the offer. The surcharge for one large and one small barn door, which will be glazed, as well as 4 normal windows is just under 1,400 EUR. We are only having the ground floor equipped with this; the upper floor only has smaller windows. Unfortunately, we have to/want to decide by tomorrow, otherwise the barn doors (aluminum) will cost 11.5% more due to a price increase. The window manufacturer has requested a sample glass for the sun protection glass, but it has not arrived yet. He said the appearance would be the same as with the thermal insulation glass, the color is "neutral" and should be like a normal window. I think we will probably take the risk. It makes me a bit uneasy not to have seen it beforehand, but I think even with a sample glass the darkening effect due to lower light transmittance would be difficult to assess. Since we receive light in that area from three sides, as well as additionally from above (steel window from the office into the gallery), I hope that will be sufficient. I will report in due course.

Again: thanks :) Then we will probably do it that way. Unless the extra cost is manageable.

Of course you can see that. Once looked out of the conservatory with the door half open. So once without glass, once with. Even with normal triple-glazed windows, you can see that it is darker.

Not with super decolorized glass. There you have no color deviation and only minimal darkening. But most people probably have never seen that.

With sun protection glazing, you always see a darkening in direct comparison. But it is not extreme.