Look up harris stay brite #8 if you think brazing is the only way to join copper and have it hold up to r 410a pressures, we braze at my work but I know of plenty of guys who use stay brite #8 with great success.
Linesets, fittings etc are and have been the same no matter what refrigerant is used, refrigeration fittings are typically long sweep 90s and thicker then plumbing fittings but a refrigeration fitting is a refrigeration fitting, nothing changed with them with the swap to r 410a. Most of them we can get now come from overseas so I highly doubt they are better quality then what was available 20 years ago.
In some cases a size change in the lineset may be needed, more due to manufacturers looking for every bit of efficiency then a change in refrigerant, we saw this in 3 ton units a few years back with a bump from 3/4" to 7/8" suction lines, fast forward and most of those are once again 3/4", go figure.
I went to a class on a new 25 seer inverter condenser and the lineset requirements for that are very interesting in order to maintain proper oil return, verticals different size then horizontals among other things.
We have been installing r410a units for around 15 years now, we replace linesets when we can and flush the ones we can't. We will not use a 410a condenser with a coil that was used on a r-22 system unless the coil is AHRI match with the condenser and we feel we can properly flush all the oil out, most of the time a new coil is a better way to go by the time you add in the cost of the flush kit and the time needed to do it.
I've installed a handful of the dry ship units, we will only use these if we can get an AHRI match up, typically we would use one if a r-22 condenser was damaged due to tree falling on it or the coil was rotted out from dog piss.
Yes r-410a is a blend, yes it should always be charged as liquid and in theory the entire charge should be pulled and replaced in the event of a leak, in practice I've never even heard a rumor about somebody having a problem due to topping off a r-410a system, if anybody has any real world problems that are due to topping off a system and nothing else I'd like to see them.