Actually fund house diversification is not really that important in my view because underlying instruments are majorly the same.
It’s just that I don’t feel like seeing vanguard everywhere in my portfolio 
that’s all. In addition they are not really cheapest in UCITS range. See here
For detailed review of Swissquote, read this
ETF leaders -: this link might be best to check our various ETFs available on Swissquote. Somehow the link doesn’t work when you click it but it you click products and then ETF and then ETF leaders , it would work. Kind of strange
Best to use ETFs available under „ETF leaders“ as they are available at flat fee of 9 CHF while others are more expensive to trade. I normally use only SSAC or SPDR ACWI on Swissquote to keep life simple.
P.S -: since SQ is obviously much more expensive versus IB. I tend to keep number of trades minimum.