Izure Saikyou no Renkinjutsushi?

Both MCs use their knowledge of another world to create items in this fantasy world! They both just want to create what they enjoy while living a relatively slow life. Their skills don't go unnoticed though and they are dragged into ALL kinds of drama! 

Both have alchemists with good slice of life progress. Good story & world building. Though ” Possibly the Greatest Alchemist of All Time” has more fights in it both are great with likeable characters & good animation. If you enjoyed one you will most likely enjoy the other.  

both have working adult MC isekai into a teenage body both have slaves although one treat them like employees and the other family both try to live the laid back life but are too overpowered while Takumi from alchemist his more upbeat Satou more calculating so able to hide his op skills easier and while Takumi seem oblivious to his haremettes feeling satou most likely know their feeling but act likely he doesn't because of the the mental age difference  

Both mains got isekai'd by mistake from gods and given bunch of op skills to live comfortably. 

Two silver haired white haired dudes are isekai'd in these fantasy adventure isekai's and learn ways to improve themselves to be of use to the communities there, one becoming a healer and the other an alchemist. They become rather well-liked by the people around them as they go on abouts their journeys. 

Isekai collectathons where the isekai'd characters grow stronger with magic for their own benefits whilst coming across a variety of different species characters as they go abouts their journeys Main difference is the difference of genders the MC's are between the two shows but the accompanied members are all female, also that the story for Renkinjutsushi is a bit more serious with more at stake in comparison to Slime 300 being a lot more light with comedy but they do have heartwarming moments in both too