Common options:
1: Tint up to the top electronic line on the back window only
2: Tint the full back window including the roof
3: Tint the front roof window (With or without either of the back window options)
Doing #1, you cannot see any difference from the outside and from the inside you can only see the darker section if you look that way. It's not apparent in the rear view mirror. But it is there overall. However some tint shops can/will only do this and not the full panoramic roof.
Number 2 will avoid the transition line, but some shops cannot do it, and many that can will have a difficult time doing so. That's a lot of glass.
Three out of four shops nearest me would need to use two separate pieces of tint to do it.
Tinting the full roof glass...
Generally doesn't reduce heat that much.
Doesn't affect UV by a relevant amount. The glass in autos already blocks most UV.
Doesn't actually (in most cases*) reduce the VTL that much. VTL is multiplicative, not additive. That is, 50% tint and 50% tint together does not block 100% of light, but rather blocks 75% light. So 35% VLT tint is just over 1/3rd transmissive. If it's put on 3% VLT tint, it will only reduce the total transmission by 2% of the outside levels (65% of the inside levels) and make it 1% VLT tint in the end.
(* Some tints block light in different bands differently, so the percentages when combining tint can vary some, but not too dramatically.)
Anyway, some people like the reduction in glare from above. Some people can't tell a difference when the sun is shining down on them. Some people don't like the reduction in seeing the night sky. Some people never look up in their car. Some people think it's just too expensive to bother.
It's all up to your personal sensibilities and preferences.