I'm ABC and my father's family are from northern Jiangsu. I've been learning Mandarin through a class, but I've noticed my family's pronunciation of the palatals is different. Upon further research, I found that this is an archaic feature in our specific dialect (and Central Plains Mandarin to a degree).
While the GKH and ZCS series merged in Standard Mandarin before i/ü medials, they remained distinct in the Central Plains. The GKH series became pronounced JQX, but ZCS stayed ZCS. However, in my family's dialect, the GKH series also remained un-palatalized.
For instance, 效 is "hiao", whereas 小 is "siao". 新疆 is "Sin-giang", 请问 is "cing-wen", etc.
How obvious is this to speakers of Standard Mandarin? JQX often sounds like ZCS to me, so I don't think there's a great issue with pronouncing 小 as "siao" or 西 as "syi", but I'm unsure about GKH. If I said 'Běi-gīng' and 'Giāng-sū', would I be understood? Does it sound too dialectal or 'provincial', or does the natural lack of GKH before i/ü medials make it not noticeable to regular speakers?
With whom do you plan to converse in Mandarin? Americans of Chinese descent? Or will you be heading to the PRC to speak with people there?
If you're not planning to take on a job that requires speaking Standard Mandarin, I don't see much issue with speaking Mandarin in the particular accent or dialect that your family traditionally spoke. There are some Mandarin dialects that would be only partially mutually intelligible with Standard Mandarin, but it doesn't sound like your family's dialect would be too difficult for Standard Mandarin speakers in the PRC to understand.
From what you've described, other Mandarin speakers would clearly know that you're not speaking Standard Mandarin, and if you are relatively young, they may correctly deduce that you are a heritage speaker of Mandarin in the overseas Chinese diaspora.
I was planning to go to China sometime later this year, so I'm worried about what Mandarin monolinguals would hear. For instance, if I said 学习 as hüé-syí like my family do, would someone in Beijing or Shanghai understand me? I'm just wondering if I should manually try to merge them together into X or if the vowels make it understandable.
Are you going to be living long-term in China? Is your grasp of Mandarin structure and written Chinese otherwise good? If out of the blue you just say "hüé-syí" people may not understand. But if you say it as part of a sentence as part of normal conversation then there's a high chance a native PRC Mandarin speaker would understand you.
You can always learn how to speak in Standard Mandarin, but unless you put a lot of effort into it, people would likely still notice your accent from your family's dialect of Mandarin.
Native Mandarin speakers in the PRC are surprisingly adept at understanding even quite thick accents from various Mandarin dialects, much better than any non-native learner of Mandarin can discern. If anything, you may find other learners of Standard Mandarin (Hong Kongers, overseas Chinese diaspora, foreigners, etc.) to have more trouble understanding your accent or dialect.
I think in PRC if you j,q,x just as z,c,s you will be understood 100% by all it is no problem. do not say g,k,h it is too hard but easy to remember because j is z and q is c and x is s please remember this
I always have pronounced the j,q,x sounds as the same as z,c,s. just remember to say the g as z and k as c and h as s when before i or v. this is sort of female though be ware