Sage 100 v2022 was released in April 2022, and Product Update was released in June 2022. I would highly suggest "testing" what you are planning.  Importing 1M Records could take a very long time, and it will significantly slow down processing of all tasks related to inventory.  I'm not sure what business needs 1M item codes, and is still on Sage 100.  Your network will have significant impact on the tasks.  Are you talking Standard, Advanced, Premium, etc.  

Advanced, and we have multiple vendors with 150k+ products, we do not sell them all but, scrubbing the product data is the issue.  Importing a whole catalog would be easier on our side.  If Sage can not handle that many products without any system lags then we will have to filter down the products to only ones we have previously sold.  New products sold that have not been imported will just have to be entered one by one.  Some of these vendors offer API integration to their product catalogs, would setting the API up and Sage automatically creates the product when a user selects the item be an option?  We map the fields and it can look through the API for the item code?  Then import the other valid fields? 

I think the main lag would be just the initial import. When you look up items, if you can use filters to look up the data, you should be fine. The real data entry is in Sales Order and Purchase Order.

Fyi to anyone with this situation, it has taken over 8 hours to import around 500k item codes (we did have to run 2 imports to associate the item codes "IM1220-DSD enhancement"), being tested on 2022 Premium.