Is it enough to plant borage two feet way or should it be closer for best effect?
I think maybe there's a recent thread here where Borage was mentioned as a companion plant and there were mixed feelings about that in terms of what some folks said what it's supposed to do as opposed to what it actually did in their gardens, which was nothing.
I tried companion planting with Borage many years ago when Louise Riottes book called Carrots Love Tomatoes first was published and it was the wrong thing to do since I save seeds from many OP varieties, Borange can draw insect pollinators which can then be involved in cross pollination.
it's been said here and there that Borage can improve the taste of tomatoes and also increase yield, but IMO that's hard to swalllow.
And most of the time folks don't use the same variety with a specific companion plant and the same variety far away, as a control plant. Withno controlplants of the same vareity no conclusions can be made, and it has to be done in the same season as well
So I can't answer your question asking if Borage can be 2 ft away or needs to be closer since personally I don't think Borage is anything magic.
But I do love those blue flowers, there's a whitge Borage as well.
What effect are you looking for?
There are claims borage deters hornworms.
I planted borage near tomatoes five years ago. From the little I remember, something ate the borage when it was quite small, and I haven't tried again.
I only planted borage once in my garden and it has come back every year since. It's not what I would call an invasive, but they do self seed readily.
My borage variety gets huge needing to be cut back just to keep it in bounds so planting closer than 2 feet would mean it would be inside the tomato plant.
Mine is not planted as a companion plant, just in the same area when I rotate the tomatoes from year to year. I haven't noted any special benefits.