Difference between Watts 800M4FR & 800M4QT?

Im hoping not to have to hire a plumber again, although I think that I will. Any ideas what is happening here? 1951 house I bought and been living in since 1986. Twice between 1986 and 2012, the main sewer line got blocked by roots and i paid for a professional to snake it out. After the 1st time, I left the drop open (covered by loose wood) so if it backed up again, it would come out in the yard and not in the shower again. That made clean up much easier when it got clogged a 2nd time years later. Then many years later, in 2017 we had/have another issue. This time it was just a main line slow down. It cleared up and then slowed down two more times in less then 30 days. During these slow downs it did back up out the drop into the yard. Between the 2nd and 3rd slow downs, the toilet, sink, and shower in one bathroom backed up. I fixed these with a plunger in the toilet. Then a week or so later the main line got fully blocked and I had to call a plumber who cleared it out (aug 2017) and said that the block was just 20 to 40 feet from the drop. He stopped snaking when the clog cleared. Then about 2-3 months later the bathtub in the main bathroom occasionally gurgled for about two weeks. I plungered it several times. Then the main line got clogged again and backed out the drop. This time when the plumber came (nov 2017) i had him snake all the way to the city pipe, which is a few hundred feet. Then all was fine...Until a few days ago that I smelled a stink in the garage, but just one breath. Sniffing around trying to smell it again and I cant. that happened many times for 3 days. Each time it is just one wif in the exact same area of the garage, one wif, then it is gone. I smelled the wood covered drop and nothing. Then I started smelling it, but much stronger at the window in the main bathroom. I sniffed and smelled nothing at the toilet, sink, and tub drain. So, I went outside and cant smell it on the outside of that window. This window is near the drop. About 10 feet from the window I get a week wif of this stink. I get down and I cant be sure, but I think its coming from the ground. I walk all over this area and it is not mushy or caving in. This went on for a few days. Strong smell inside the bathroom by the window, no smell outside by the window, weak smell in yard about 10 feet from the window (where the main line might be), no smell at the drop and no backup at the drop. Also, no smell from the tiolet, sink, or tub drains. Then last night I took a shower in the main bathroom and the drain backed up. I had to plunger it several times before it drained. Since then no smell...anywhere. I had showered the last few days which was after i started smelling stink in garage and the drain worked fine then. This seems obvious that it is the tub pipe before it reaches the main (maybe same area of yard where I smelled the stink), although when i 1st got the smell in the garage the tub drain in main bathroom was working and no stink at bathroom window. Also, if this is related somehow to all the issues since aug 2017. BTW these four times are the only times Ive had a plumber here and Im sure that I've used my plunger less then 10 times since I moved here. I'm thinking that maybe I should dig up the yard. I still might need to call a plumber, but if I can save the labor by finding the issue and clearing away the dirt and later filling it in, that is good, however, I do sometimes make larger then needed projects out of things. The last time plumber came, he said 500$ to run a camera thru the line to find any pipe issues and then 1/2 of the 500 will go toward any work done. maybe I should just do that. I do need to move on this because I really dont want to wait for the main to back up again. Money is tight so any way I can reduce my expense is good. Note diagram heart is where I sleep and that grey window is always open and I never smelled anything. Thoughts? pa

I have a single family house on city water pressure that has an issue when multiple things are using water. For example if the washer is running then the shower will only have a little trickle coming out. If showering and someone flushes a toilet then only about half as much water comes out of the shower. It's lead to some funny times when someone is in the shower and another person puts a load of laundry in only to hear yelling come from the person upstairs. As funny as it can be sometimes it is a nuisance and I want to remedy the situation. I thought at first that this was only a pressure issue but used a pressure gauge at the first connection I could find on the main line coming into the house and it is OK. After taking a closer look at where the water comes into the house there seems to have been an old repair at a 90 before the first valve inside the house. Right after the 90 the copper pipe necks down from 3/4" to 1/2" and then again to either 3/8" or 1/4" from what I can tell. It is only a short little section but I think that may be causing my issue. I know I'll need to call the city to shut the water off to my house while I replace the section of necked down pipe but before I go through all of that I'm wondering if I'm on a wild goose chase or actually may have found what has caused my issue. Can a small section of necked down copper piping as it comes into the house cause what I've described above?