There will be a Tarriff and regulatory border between NI and GB following implementation of Boris' deal after the transition period, end of December 2021.
In practice it will be a paper based border with all goods leaving the UK mainland heading for NI being subject to tarriffs is they are deemed "at risk" of entering the EU.
These two articles discuss the situation.
Prof Alan Winters, the director of the UK Trade Policy Observatory, prepared an analysis of the deal as part of ongoing litigation taken by anti-Brexit campaigners.
The campaigners, led by barrister Jo Maugham QC, argued that the deal contravened legislation preventing Northern Ireland forming part of a separate customs territory to Great Britain.
Prof Winters' analysis concludes that, when considering both Great Britain and international goods, a total of 75% of Northern Ireland's imports could be subject to EU tariffs on arrival.
But will it create barriers between Great Britain and Northern Ireland?
Yes, but the DUP has accepted that regulatory alignment with the EU on goods and agrifood will help keep the Irish border open and maintain peace.
Neither discusses any border infrastructure, most likely this will be restricted to checks at ports to ensure that the filed paperwork matches the cargo being loaded. Similar to checks that will be put in place between the UK and European mainlands. The final details of which are unlikely to become clear in the near future.
The big caveat for all this, is that this is Boris Johnson's current Withdrawal Agreement. And a new general election is under way. If the Conservatives do not win a majority, then all this will be meaningless, and either we'll be looking at an entirely new Labour proposal (to be voted on in a referendum), the whole thing scrapped under the LibDems, or a WTO Brexit as baseline with a Tory/Brexit Party coalition.