Clearing Customs in the Initial European Airport

Mike, I think that Transat will be offering a seasonal direct service to Prague later this year... if so, check out their Club Class fares.

It's going to depend on the connecting airport and you've listed so many that work differently that it would take a book to describe all of them.

Essentially, with checked bags, you probably won't hit customs until the final destination when you catch up with your stuff.

Immigration may not happen when you enter the Schengen Zone unless you leave the sanitized area of the airport, but it probably will.

Some airports will have additional security checks just short of boarding, even if you remain in the secure area.

If you've booked it as one continues journey, which is apparently what you're looking at, you have to assume the connecting times are adequate. If the carrier balls it up somehow, they'll stick you on the next available departure. If you don't have a very late in the day final destination arrival, it won't even screw up the first night's reservation since you're heading to someplace like Prague which has numerous arrivals every day.

You would not go through customs or immigration if transiting the UK but transfer airside.

In the others you would go through immigration and customs for your hand baggage, but anything through-checked would go customs in Prague.

If connecting in Schengen zone you will go through immigration only. In Prague you will go through customs. It's total formality because your flight to Prague is already from Schengen country and immigration officers don't know that you are coming from outside of Schengen. There are two gates out: one with green light - nothing to declare and one with red light if you have something to declare. I think it's clear which gate you should choose. Theoretically they can stop you at green light gate, too but I haven't seen it happen, yet.

I agree that it would be wiser to allow more than an hour. Suppose your departure is delayed? Most likely the second airline will have other flights to Prague, so consider using an air-search engine that will let you specify more choices. I agree with the previous posts about Customs. Sometimes there is a random-selection search on a Green line (often just an x-ray of the bags) more for safety screening than for contraband. I can't think of the last time my bag was opened. Maybe I've been asked if I had alcohol, but I never have any going in.