"Tubular" I can at least trace where it came from. It's surfer lingo. Sometimes when you catch a wave, the wave crests all the way over you and encloses into a tube. Surfing through that is supposedly the most euphoric thing about the sport. "Tubular" is thus "anything that makes you feel the way a surfer surfing through a tube-shaped wave feels". Thrill, wonder, excitement, etc.

I have no idea where tf "based" came from. Wiktionary suggests that it ultimately comes from the chemical definition of "base" (i.e. the opposite of an acid). "Freebasing" is a way of converting certain drugs, particularly cocaine, into smokable form by converting them from acid to base. Rapper Lil B. is alleged to have coined "based" to describe his lifestyle as someone who is unafraid to be himself as an individual (which, I guess, included smoking crack). This supposedly filtered into 4chan to become an alt-right slogan for "admirable person who bravely maintains alt-right opinions in spite of adversity" ("based and redpilled"), and later was claimed by groups outside the alt-right to simply mean, "someone with admirable opinions".

My closest guess is "based in reality".

Doesn't Tubular mean "reminiscent of the Mike Oldfield track"?

I've started just blocking all the idiots who use it.