solo 401k question

[nic1]

I am starting a 1099 position in addition to a w2 position that I work three days per week. 
I have a 401k offered that does not have a match at my W2 position. 
I would prefer to open a solo 401k since I have the 1099 position now and put my max contributions for the year in that as opposed to the 401k my employer offers.  employer plan has higher fees and crappy fund choices and I would like to set up solo 401k through vanguard.
So my question is can I have a solo 401k if I have access to one through a W2 employer?
We also max out my husbands tsp as well but for funds in addition to that would like to have a better plan. 
Also thinking about trying to do a back door roth this year but I know our expenses in retirement will be probably around 40k less per year (kids childcare expenses and mortgage, which will be done with in retirement for us) than they are now so in turn our income will be less and feel like the tax break while our income is high is preferential.
Thank you for any help.

[chucklesmcgee]

You can have multiple 401ks, however my understanding is that your combined annual contributions to them cannot exceed the limit.  So if there's an $18k contribution limit for you, you cannot contribute $10k to one 401k and $10k to another. I'm uncertain if employers can individually contribute their limit or if there are additional caps as well.