I usually do it the same way you do it when it comes to getting a MAX Value for joining purposes or display purposes (like Last Approved Revision). I typically have much more Sub-Queries bundled together, it makes it much easier.
But if your Query is as simple as it looks, Sub-Query will prob be the best.
But just if you are curious, how a Sub-Select works in BAQ here is more info:
The beauty is you don’t even have to display it to use it in a JOIN, let’s pretend you have SubQuery2 that is a TOP 1 and returns only 1 column. You can just enter it in the JOIN Criteria.
There is always a time and place for it, depending on complexity, and speed. Typically a Sub-Query (not a sub-select) will be faster, but if you are grouping stuff and have groups after groups after groups and wrapped into many queries, its tough to maintain.