Of course you'll find enough monuments and historical sites in both Marrakech and Fez, these are the two oldest cities in Morocco, so don't worry about not enjoying your trip if history and culture are what interests you! for the plan, there are many places you could visit in both cities, in Fez there's the Medina, which is the oldest part of the city (Fez is big city with more than 1.1million inhabitants) I'll suggest you take a a Riad in the Medina and enjoy its beauty. it is safe but be careful and know that you'll be suggested a lot of help by many children that are not willing to help you but be your guide and expect money in return. so my advice is to either plan well your trip and know what you'll do and only ask for directions from salespeople that you can trust from the looks (there are many) or be ready to lose much of your money on tips plus a headache with those children who don't know what enough is. in Marrakech it's somehow similar but different, people are more difficult and salespeople are the biggest danger haha. they want to sell you anything just to take money. if you go to Elfna, you'll find showpeople with snakes and monkeys, be very careful there as they'll put a snake on you so that you take a picture and pay them. They'll even try to take money from you if they only see you taking pictures. if that happens that off your smile and act like your getting angry because he asked you that otherwise he'll be the one playing that game acting all angry and weird. Use a firm NO and try to minimize the touristy look if possible, and also try to look like a traveler who knows what's up and is tough himself, and that with everyone when it comes to Marrakech, don't always be mean but show them that you know what they want and you wont give it because you're smarter, otherwise they'll think they smarter than you and that's the worse you can do for yourself! I'd recommend you take a look at this itinerary guide, it'll help you plan your trip to Marrakech, and the traveler's profile has also a guide to Fez, I'd recommend you check that one as well, it covers most of the must-see and do things. I hope you'll have a great time! Here's my suggested article
https://tripblan.com/trip/marrakech Cheers