Bookkeeper: I recall reading that the Me-262’s wings were swept back when the engines were changed, not the undercarriage. It says here that the wings were swept when the unreliable Junkers Jumo 003 engine was replaced with the heavier Jumo 004. Same reason, though – the center of gravity would have been too far forward, so they swept the wings back. The prototype was a tail-dragger, and I guess it must have had straight wings.
Yep…and much more modern ones than you listed such as the A-10 Thunderbolt (aka Warthog).
IANAAerospace Engineer but it would seem anything meant for low and slow flight benefits from straight wings with swept wings benefiting faster planes. Where the changeover occurs but at a pure guess it seems when planes start being meant to fly over 350 mph (WAG) you start seeing swept wings.