@Travel4Fun, below is the CURRENT situation at AMS Schiphol based on my four flights through there in the last 10 days. These thoughts are based on the NL rules, yet you need to read through the Egyptian parameters as often ENTRY into a country is determined by where you've been in the previous 10-14 days. (And you don't want to exit the AMS airport if that impacts your ability to enter Egypt).
Will I be able to leave the Non-Schengen part of the airport to see Amsterdam during the layover and be able to return to the Non-Schengen part of the airport to continue to Egypt without an issue?
Yes, you will be able to exit the airport, enter the NL, and return, as you have proof of vaccination and a negative test. Simply exit your plane and walk towards the Arrivals area (Baggage control). You will have to clear immigration (passport control), exit through the Baggage Carousel area, and enter the LANDSIDE section of the Schiphol airport. Once there, you can purchase a train ticket to Amsterdam Centraal or take a taxi, bus, etc. to the city.
Will the negative Covid-19 test that I took in the United States within 72 hours qualify once I leave the airport to visit Amsterdam
Considering what I want to do what are some tips to minimize any issues/problems I may have?
In advance, complete the NL Traveler Health Declaration Form - you can find it online. (I've only ever had to show my once in my last 10+ flights through AMS, but it is the current requirement). Give yourself plenty of time for your return as you will have to go through security and passport control on your re-enter AMS. Having a boarding pass in advance for your second flight is advantageous - if possible - as you can simply "scan in," and head for security. Once you clear that, then passport control. Finally, you will walk into the Non-Schengen terminal area of AMS. From there, simply walk to your gate.
Referencing @thenosbigs comment on purchasing food in a restaurant, yes, you are supposed to have an EU Digital Certificate to enter a restaurant, cinema, cafe, etc. That said, I have spent the last few days traveling with Americans in Den Haag, Maastricht, and points south... and their CDC cards were accepted as NONE of them had the EU Digital Certificate. Perhaps near the airport, the restaurants were following the "letter of the law" but frankly, we've only been asked for our pass about 50% of the time. I suggest you show your CDC card - or move on to the next restaurant if it's an issue.
So yes, this can be done - just watch your timing... and check on the Egyptian entry parameters coming from an EU country.