Using any weighted system, boat speed is always the first thing to adjust a weights dive level.
But, trolling with/against/across Lake Erie currents also changes the dive curve. So you could calculate and guess your dive depth. Add in your line type/size.
IMHO, a faster. more accurate way is to...
Get your boat at your wanted trolling speed. Attach a 2 or 3 oz weight to the snap on the end of your line. Lightly thumb spool (in free spool mode) till your weight touches bottom. That right there typically will put you 3-4 ft above bottom once the weight matches boat speed. Depth of the weight.
Any more line and will probably having your deep diving bait touch/snag bottom. Reel up a couple feet. That will be your max lineout. Divide that lineout into how many rods. Now you are able to cover the water column. Adjust lineout as required. Depending on where you place a snap weight 10,20,50ft a deep diver will typically 6 to 12ft max deeper than the weight.
Doesn't matter if you are using snap weights or inlines or dropper weights. Works the same. Just a slight difference in how much deeper a bait dives than the weight due to the line past the weight.
Once you learn/remember your average lines out. You will know what to set everything to when headed out.