I’m looking for a base layer that helps keep me warm when the weather is cool, but helps to keep me cool while it is warm. The only thing is that I am not at all knowledgeable about what all is available. Also, I’m really wanting more of a long-john style base layer that is all one piece.
Have you considered heated base layers? they’re game changers for cold weather and you can adjust temp as needed (just turn off when warm). You’ll need a portable power bank though - gearscouts.com has good options for the batteries if you go this route.