Yes you can upload as many of these as you wish, as long as you have enough storage in your ReportServer database. You do however need to think about how many might be in use by users at any one time however.
When a user views a report the PBIX file is unzipped into memory (RAM) and a copy of the "imported" data model is spun up in a captive SSAS instance. So for a 1.5Gb PBIX file you're going to get that 1.5Gb loaded into a hidden SSAS instance. The SSAS instance needs some memory to run in (let's guess at about about 1Gb just to run in?) and it then needs an additional 1.5Gb to load the data into. You probably also need another 500Mb - 1000mb for queries being run against this data. The more users you have querying any given PBIX(model) the more query space you will need.
If you assume 1.5Gb + 0.5Gb query space per model thats 2Gb. If you have 10 such models you will need at least 20Gb RAM and the 1Gb needed to run the underlying SSAS instance, so 21Gb and ideally a decent slice more than that to have users viewing them all at the same time. So you need to ensure your PBI-SSRS Server has plenty of memory. If the reports are only being viewed by a small number of users or you aren't viewing them all at the same time then you may be able to get away with less as the loaded models get disposed of if they are unused for a period of time. How long they get kept in memory "just in case" is governed by a timeout setting on the server.
As long as you plan for this it shoudln't be a problem.
