I am a bit older than you (about 40 years) but here goes.
Started working life as an electrical fitter apprentice - motor winding, building switch boards, machining (shafts, bearings, commutators etc), building HV trannies (electrical ones), welders, we did anything that came along.
Late in the 2nd year of the apprenticeship they found I had a bent for design and placed me with the 2 company engineers and I spent the next 2 years designing some pretty massive control systems (all hard wired), switch boards, welders and HV trannies. During the whole period I was also sent out to do service work on machines (trouble shooting).
Absolutely impossible to get this whole range of experience in one place these days. The whole industry has become fragmented ('specialised'). We even did plate and tube rectifiers, Xray machines, humidicribs and anything else that came along.
Go to a factory in the middle of the night, machine broken down, no drawings, not much help from the operators as to the problem with the machine as they would rather sit on their tails than work. Marvellous experience.
Moved into technical sales, management, sales and marketing for 25 years.
During all these years I did an engineering certificate course, electronics course (transistors were the new buzz word), slaes, marketing amd management diplomas as well and selected intsrumentation courses.
Saw a lot of the working world from all sides and I found that the guys on huge money were doing everything. Auto glass factory here in Ozz the electrical technicians were maintaining the plant at night - no fitters, plumbers or anyone else just 2 of them. They were doing all trades work as well as electrical and PLCs. They were on huge money.
Went to work for an electrical contracting/switch board company - back to the trade - designing control systems etc - in fact systems integration.
The thing I like about SI is that it is varied, challenging, frustrating, you name it. Basically almost anything can lob on the desk and you just have to design it and get it to work. A lot of investigation is required to obtain the right equipment to do the job. It is great. I was the only one in the place doing this and invariably working on up ti 15 jobs a day. Investigating, designing, writing software, commissioning, organisng gear, supervising switch board and contracting staff - sometimes from thousands of miles away when commissioning a power station or something simple like that. Good fun.
You will find things a fair bit different in an SI house. There is usually a fair degree of organisation and people are assigned different tasks. For example, on a large project there may up to 20-30 peolpe working on a job with several team leaders. One area working on design, anoyher on PLC programming, another on SCADA etc - depends on how big the SI house is and the size of projects. I know many working in large and small SI houses.
A small SI house I could live with as there would usually be a fair amount of independance - a large SI house would drive me nuts - too splintered, spread sheets going back and forth, meetings, too organised. I cannot work that way but many can.
Since I have been working for myself doing the lot myself - design, build panels, programming, SCADA systems, commissioning, accounts, paper work you name it. I do have sub contractors that I trust and also sub contract to them as well.
If you can think on the fly, have varied experience in all sorts of things, have a bent for design and software, like living a hectic life with lots of stress meeting deadlines you will almost certainly enjoy the SI life in a smaller company. You will find you will need to be very well organised, you will need to get on well with people, be diplomatic and, at times, have to stand up for yourself and your company. Unfortunately in theses days where evryone wants to sue at the drop of a hat, apportion blame to everyone else when they are in trouble/behind on the job you will also probably have to be a lawyer as well. You will probably have to know the OHS&R laws, contracts, insurance etc etc. It is a very broad life experience.
Very good luck with your new experience. If you can stand the pace and learn all the law things you will probably really like it. I know I have absolutely no regrets about my varied life/work experiences.