Gueye I think Walsh might be judged in later years though on how Calvert Lewin, Onyekuru and Vlasic etc progress
I think you're right, but I also think it's already fair to judge Walsh now personally. We see teams getting lucky all the time, with decent results covering up pretty poor performances. In the long run though, if you're putting in awful displays on the pitch, the results are probably gonna turn ugly. We're seeing that at Everton now and I think you can easily extend the same argument to transfers.
The players you've mentioned were all teenagers and been putting in decent showings in and around first teams for a couple of years. That's generally a pretty good sign of future success. So I'd call all three - and Lookman - good signings right now.
There's loads of reasons why they might not work out. Injuries, they might not settle, they might have tough (and established!) competition for places. So, even if they're not first team players for us 4 or 5 years down the line, I'll still probably think of them as a good signing in terms of process.
You can caveat Walsh's performance as DoF with loads of explanations/excuses, but if only around half of the signings seem to have a decent process behind them then something has to change.