The answer is obvious, so you have to wonder why ask the question?
Is sex the same with civvies and SPs? Well, yes, it's sex. I'd be disappointed if I'd never had SP style sex with a civvie, but for the most part it's like the difference between watching TV on an old 14" portable or a 50" UHD, it's still just TV though, you wouldn't say you've never seen TV if you've only ever seen an old portable.
Is popping your cherry with an SP the same as popping it with a civvie. Shit no! Like your only sex education was through watching porn. The first time you have sex it's going to be a nervous, awkward experience for both of you, with an SP at least one of you knows what's happening. Your first time with a civvie is going to be much the same whether you've already had an SP or not.