Realistically there can't be much of a border between England and Scotland, same as there can't be between Ireland and Northern Ireland. It's just impractical to put to a wall, border check points and the like.
It'd certainly be awkward but there may not be an option if the EU insist on it - as they might do, to avoid people dodging the EU tariffs by using the UK & Scotland or Ireland as a back door. Avoiding one certainly wouldn't be automatic.
In any case, some would argue that tariffs with the UK are worth it to stay in the EU.
That would be an odd view, given the relative importance to the Scottish economy of UK vs EU trade, and given that far more Scots live in England than in rest of the EU. But as we've seen with Brexit, politics can trump economics and practicalities, who who knows?