There is no maximum product limit on Shopify. You can upload as many products you want.
However, there is upload throttling once your store reaches 50,000 products. After 50,000 products your store will only be able to upload 1,000 products per day.
If you need to upload more products per day, you can upgrade to Shopify Plus which does not have this limit.
If you cannot afford Shopify Plus, you can use an app like Bulk Product Generator. Run this app 24/7 and you can generate 365,000 products every year.