I’m aware that ‘this’ is used for a singular thing while ‘these’ is used for plural. However, I also see people who use the phrase ‘this two’ so I’m not sure which one’s correct.
"These two" is correct because two is a plural, as you say. The only sensible exception I can come up with is in a very specific verbal discussion.
A signwriter is having trouble deciding how to write a numeral, so he calls a colleague over.
"I'm trying to find way to make this price signage really eye-catching. So which do you prefer? This two," he asked, pointing to a curling, cursive numeral, "or that two?"