Bug BUG-000105837 is more of the Server/Enterprise documentation not telling you of the suggestions limitation with geocode services that you create from your own locators. The suggestion limitation was resolved in the Esri World service last June. We will be including info about the limitation for customer created geocode services in the documentation for the 10.6.1 release.
Bug BUG-000094346 is regarding invalid house numbers and suggestions, this behavior exists for all of the out of the box locator styles that search for house addresses in 10.5.1 & 10.6, more discussion and details can be found at https://community.esri.com/thread/164282#comment-717731. We are actively working on making the suggestion fixes in the Online service available to customers when they create their own locators and services, but do not have a time frame for when it will be released. If you want to be able to search just on street name and get suggestions for street names, it's recommended to use the Street Name style.
I have not seen any reports regarding the geocode service memory leak based on a Single Field locator w/o suggestions. I would still suggest using the Gazetteer locator style to build a locator with suggestions and use it as a geocode service to make use of the spelling logic that is not in the Single Field style. The leak for the Single Field style based geocode service is not resolved for 10.5-10.6.
You may find this info helpful for creating a Gazetteer locator https://community.esri.com/people/cdufault-esristaff/blog/2018/03/02/gazetteer-geolocator-best-pract...
