for a discussion of this very topic.

In her case, she lost track of which account she was on, with almost calamitous results.

You raise the point of whether these SM sites can mix things together. FB has been doing just that for years.

I council that no one should use SM for the hobby, but I guess SM is here to stay in the hobby, so we have to be very cautious about using it.

Two phones would be the way to go.

Search that subject line, "Social Media: Avoid Like the Plague That It Is" on General, Newbie, S&P, NY and Boston going back several years. You'll get lots of threads and discussions of near or actual disasters that occurred when Real Life and Hobby Life crossed unintentionally yet unavoidably.  
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Minimally, use two different phones. Try to avoid any crosstalk between accounts in any way, shape, or form.  Do not access BOTH accounts from the same computer. If you do, don't be surprised if Hobby You and Real You end up "friending" each other (or whatever it's called). If that happens, watch the tentacles start to ensnare and mix up friends and contacts from those different worlds with Real You and Hobby You as the only common denominator.
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The stated purpose of  FB, Google+, Twitter, Snapchat, .... is TO CONNECT EVERYONE ... WHETHER THEY WANT TO BE CONNECTED OR NOT!  They are very good at it.
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Good luck! Stay safe! And Private!

Given the push to convergence and full-on connectivity across platforms and programs, eventually all of your contacts will be cross-referenced (at least, that's the goal of the folks who make and sell devices/programs). I assume that this will happen and thus, have NO social media accounts (yes, I'm a paranoid old fart in general and has only some connection with my p4p participation).

Our privacy is evaporating faster than the shelf ice near the poles -- do what you can to protect it and leave as little imprint as possible.

You do Not need a second phone...  several apps provide free lines that differ from your main number that provide annonimity... check out burner app for an example

I'd recommend going to the website in your phone rather than downloading the app. Its not as convenient or streamlined, but will save you a headache.

With an iphone you have much, much less control over what it's doing. It's made to "just work" for 99% of everyone, and you're in that 1% that might want it to work differently.

 
Burner apps are available for iphone, and the "burner" one in particular I know works well and won't mix your contacts. It's like 5 bucks a month for unlimited talk/text and you keep the same number as long as you'd like.

 
On the topic of suggesting friends and general opsec (operational security), that's likely possible as long as you have 100% different content between accounts. That's a tall order granted, but possible. You can't have *any* of the same friends on both accounts, which will keep suggestions at bay; It won't make the connections if they were never there in the first place.

Outside of that, the best way to keep separation between your accounts is to create a persona that is notably different from the "actual you". If the real you likes roses, the synthetic you likes daisies, you get the idea.