I think the Bucs are more likely to be the 3rd party than the Browns. The Bucs have pick #7, pick #38, and then nothing until pick #102. Based on past trades I think it'd look something like this:
Bills trade 12, 56, & 96 to the Bucs for 7 (14% premium, a little above typical for a 5-10 pick)
Bills trade 7, 22, and a 2019 2nd for 2 (37% premium, a little under the Jets' premium, but above the typical premium from 2011-2017)
Bills would have picks 2, 53, 65, 121, 166, 187 (122.42, down from 167)
Giants would have 7, 22, 34, 66, 69, 108, 139, and our 2019 2nd (192.15, up from 157.85)
Bucs would have 12, 38, 56, 96, 102, 144, 180, 202, and 255 (122.25, up from 111.97)