Requesting Help with Playing Riven; Or Should I Quit Trying And Find Someone Else?

I want to play as Riven because I like the concept of getting extremely fed with her; she's also thematically fun to utilize. It's for the fun of it that I got into playing Vi for jungle.

But I'm still having issues in top lane with her. Like a LOT of issues; namely the aforementioned concern and experience that a fair amount of top laners are really tough for her to take down. She also suffers a LOT from being even slightly behind IMO.

As an example, the last two matches as Riven: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1700140762/203289894?tab=overview and http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1700093360/203289894?tab=overview. There are other matches in the history with Riven getting curbstomped.

This is why I feel more comfortable playing Garen top when I go into ranked this season. He can at least back out and regen in lane, and also still wreck face while building tanky.

You're* (i.e. any potential responses) probably going to advise that I stick with Garen for top lane and stay away from Riven if the skill needed for her to snowball lanes is too demanding. But I don't want to just play Garen or similar tanky/bruiser champions for wins because that'd be boring IMO. I want someone that can lane and snowball very satisfyingly, but also play well and stay relevant on the back foot; however, Riven currently doesn't seem like that kind of champ.

Any advice, then, on what to do if I'm ever behind as Riven (which, currently, is frequently)? This isn't a "Don't get behind" question, because there really isn't any guarantee of that never happening.

Or are there better and equally enjoyable champions for this circumstance? If there is reason for anyone to blatantly respond that my mindset just works better with different champions and that it would be better to stick with them, don't hesitate to do so.

In terms of my own playstyle: I refrain from going too ham, because I don't want Udyr/Warwick/etc. jumping on me and ruining my day. I'm more of a "safe" laner that, in terms of bot lane at least, may annoy supports when they get too aggressive and die while I back off and continue farming (not that I don't go for the kill when it appears safe, but if I see the jungler come storming down/hiding in wait, or they really start fucking up the support, I'd rather retreat than risk giving the double kill). But if it's all clear, I push and either damage the turret or back for more items/regen.

I'm less about over-complex mechanics and more about going in and destroying things. Vi - that's a champion I have at least okay mechanical skill/ a good time with. Lee Sin? NOPE. I'm cool with Garen. I'm not cool with Nidalee or Gnar, though I like them on an aesthetic level.

Thinking of making another post listing the champs I like or am good with, and asking opinion for potential good fits. Will repost onto this discussion if I get around to it.

EDIT: Re-posted this comment of mine from an earlier discussion, http://boards.na.leagueoflegends.com/en/c/tips-tricks/kf7w8LEX-riven-help-needed-and-some-champion-opinions-requested, and expanded.