In my personal experience, whenever I've tried to run multiple businesses, at least one or all of them have failed (failed meaning either zero or very little revenue)

Looking at my friends (95% of which are tech entrepreneurs or lifestyle business owners) any of them who have tried multiple businesses at once, either one or all of them have failed.

There's usually a period where you think "Hey this is possible, it's working great!" and you see a bit of growth or a bit of traction, but it's only 2 years in that you look back and realised that you have 2 projects turning over £50k each, when you could have had a single project turning over £500k

Now looking at your current situation from what you've told us:

1) Starting a business with a cofounder who is as committed as you is an order of magnitude better than starting something on your own

2) As a non-technical entrepreneur, I would advise staying away from the onlne business until you have either a technical cofounder or at least £100k in your back pocket in disposable investment

3) Does the clothing business excite you? I'm thinking not, as when something really excites you, you shouldn't even be considering anything else. So maybe neither of these projects are right for you.

My advice: go and get a job working for the company you wish you had created. Find a company where the product, industry, culture, brand... everything is something you love and wish you had done yourself. Work there for however long it takes to find something that creates a burning passion inside of you, and provides you with the right network, connections, experiences (and maybe cofounders or investors) to get it started.

My biggest regret in my entrepreneurial career is that I didn't spend any time looking at how other entrepreneurs had done it. I just read about it and dove in, and spent many, many hungry years making all the same mistakes that everyone before me had already made!