You can not apply to both Oxford and Cambridge in the same year so he would have to decide between the two. Applying strategically means to look at all his statistics and apply to the place where he is most likely to get an interview and then get offered a place. It is also about understanding that all medical schools are equal so although some might be more popular, and hence harder to get a place, the qualification is the same and the NHS will not consider where he studied in deciding whether to offer a job.
If he does well on the ucat then he might just put one BMAT choice (his favourite of Oxford and Cambridge), using his good ucat score to maximise his chances of an offer elsewhere with three ucat choices. If he does badly on the ucat he might want more bmat choices because he knows he is less likely to get an interview on the basis of his ucat so might as well risk the bmat (assuming the exam and results are still after the deadline). That would be the strategic application.
We found at this stage going to a range of open days useful so going into the ucat dd had an understanding of the sort of course and place she wanted to apply to.
Some places he will stand a better chance with 3A* predicted, some places will consider the GCSE grades, others prioritise widening participation more. As Keele put it, they are all fishing in slightly different pools for slightly different candidates.
Applying strategically means considering the likelihood of interview offers. So say last year (assuming no contextual flags), you needed 3 A stars predicted for an interview at Exeter so if he applied to Exeter it would have been a rejection pre interview. You don't know when applying exactly where the cut off will be so it probably would have been worth a shot with only 2 A stars predicted, but if he had a high ucat, there would be safer places to apply.