Well, I've never had Buff Orps or 'Lorps but my friend had a Buff Orp, Leghorns, red Sexlinks, some mixed breeds, EEs, and BCMs and her 2 Silkies had to hide most of the day behind a feeder or a waterer or a nestbox to keep away from these large dual purpose/layer breeds. The LF can be on equal terms with breeds their own size but can't resist the temptation to bully a breed gentler or smaller than themselves - it's a chicken thing! Orps and 'Lorps I understand can be sweet birds but my friend didn't find her Orp or dual purpoe very kind toward the Silkies or toward the EEs. RIRs, BRs, Wyans, Marans, Orps, Sexlinks, Leghorns (or any Mediterranean class breeds) or any hybrid egg-layer breeds are on equal terms with each other but around Silkies I woiuldn't trust them - especially in a confined run or a smaller backyard.
EEs on the other hand like our APA Ameraucana are known to be mostly non-combative hens and would prefer to flee rather than engage in conflict. In fact, that's what gives them a reputation for being jittery jumpy kooky spooky wary alert birds because they will be the one running around the yard to get away from other chickens. No breed in my flock can catch our Blue Wheaten Ameraucana once she perceives a threat and starts running on those long legs of hers LOL! She has never fought one of our Silkies even when one of the Silkies got pissy broody nasty towards her. Amer's and EE's are not the best layers after their 2nd year but they are great non-combative flockmates if you don't mind getting less eggs from them.
Might be coincidence only but I found through research some of the gentlest or non-combative temperament breeds happened to be either crested, bearded, muffed, tufted, vulture-hocked, feather-legged/feathered-toes, walnut or pea-combed breeds - Ameraucana, Araucana, Brahma, Breda, Cochin, EEs, Faverolles, Houdan, Polish, Silkie, Sultan. Out of LF breeds it is reported that Australorps, Crevecoeurs, Dominiques, Dorkings, Dumpies (short legged breeds), Jersey Giants, Sussex, etc are gentle but I still wouldn't put them with Silkies simply because of their sheer size to bully something smaller than themselves.
Spend some time on various website forums reading reviews by owners of breeds you're interested in. There will always be pros/cons to every breed but after reading several reviews a general theme starts to emerge about what the breed is really like and if it's a quality you do or don't like. Wyans was a breed I truly wanted to try but with a 50/50 pro/con feedback about them I realized they would be a risk to try in my small backyard with Silkies. We had a sweet Dominique pullet that never made it to point of lay and someday I would like to try one again to see how she does around two Silkies. I have a good home for her should she not work out for us since chickeneers are always wanting a decent layer breed. GL with your decisions and glad to see you are asking your questions and doing your research before adding any more breeds to your flock.
Wow, thank you so much for the great response!! Thinking about it, it does make sense that they would bully smaller or gentler birds - seem they bully anything different from what I've heard. And even if they didn't bully them, you have a point about size. Even normal politics could probably lead to one being hurt I suppose. Do you think it.would be any better in a larger run or free ranging? Or probably still not?
I've definitely noticed my EE's being a little spooky! Lol usually only when I try to grab them though but they all are then and I'm working on not.doing that. I've noticed the EE's and Barred Rock actually seem to be the most confident and adventurous in terms of checking things out
once they get running or.flying though good luck lol I definitely don't mind less eggs, especially since I'll have the other layer breeds and if I got Silkies, it seems I'd have to keep them separate and that'd probably mostly or entirely be a pet flock anyway. Though the layer one is too. 
