YN200 + SB700 nikon

If you want to control the YN200 in TTL or Multi mode it appears you'll need the newer YN560-TX Pro transmitter. If you only want to control manual flash power the older YN560-TX will do.

You'll need Yongnuo YN560/RF605/RF603 receivers to attach to the bottom of the Nikon flash(es) to control and fire them with a YN560-TX. Of course, since the YN560-TX transmitter is manual only, you won't have use of the i-TTL capabilities of the SB unit(s). If you use the YN560-TX Pro transmitter you can use YN622 receivers in YN560RX mode to do TTL with the Nikon flashes.

For just a few buck more you can delve into similar units from Godox. The Godox AD200 has a lot of extra features and more control of manual power levels than the YN200 (both in terms of minimum power setting and tenths of stops vs. one-third stop steps), and the Godox 2.4GHz radio system is totally unified, unlike the patchwork compatibility of the different YN radio protocols. Of course you'd also need Godox receivers to attach to the bottom of your Nikon SB flash(es) to manually control their power settings. Any future expansion into studio type monolights would also be more seamless with Godox, who offers a far larger number of options in that segment than Yongnuo does.