UTXO size for PoS?

Hello. I'm new in Qtum Staking process so I have some questions. I would glad to receive any helpful information to sort it out.
Clue by clue I found an advice to split my UTXO by a small chunks. Different sources recommend a different utxo size. It's 250  400 coins according to a first source, 150  450 coins  to second one and 500 coins  to replies on this forum. Also I have explored last mined blocks and noticed that an actual chunk size differs between approx. 100 and 1,000 coins.So my questions are:
 What is a technical reason of splitting utxo beside of utxo "lock out" period in a staking process for a next 500 blocks?
 What is a best size of utxo to improve a reward probability?
Once my wallet staking weight includes matured utxos only, does it mean that a probability of getting a next reward is different each time I'm getting a current reward and depends on a count of matured utxo at any moment? Means if I have 5,000 matured coins splitted by 5 utxos 1,000 coins each and a network weight is 15,000,000 then first time I have a weight 5,000 and probability 5,000 : 15,000,000. Once any of my utxo has mined a block it will lock 1,000 coins out so I will have 4,000 mature coins, 4,000 weight and 4,000 : 15,000,000 probability which is less than first time right? Yes, actually it will be 4,000 : 14,999,000 in a static blockchain but since it's a dynamic one we can take a network weight for a big constant value to determine a best utxo size. By this logic the best strategy is a splitting utxo by a minimal possible size to let my reward probability stay a quite constant too. A reward probability downgrading from 5,000:15,000,000 to 4,000:14,999,000 (with a 1,000 coins per utxo; for a next 500 blocks) is worse than let's say a downgrading from 5,000:15,000,000 to 4,999:14,999,999 (with a 1 coin per utxo), isn't it? If it would work like that then why don't we get more blocks with utxo = 0.00000001 coin?
Please tell me if I even close to a truth and correct me. I would appreciate any vectors of information to learn into.
Thank you in advance.

Hello Brahma,

That is the reason exactly, you lose the weight of your stake for 500 blocks, which slightly reduces your probability of winning a block reward during those 20 hours.

Your logic is right, you understand the math. There is a point of diminishing returns for smaller UTXO sizes, and I simulated that to be at the low end of the 250  400 QTUM range (I am the OP for this number range). Some other behavior that factors into this issue. Your wallet will split any UTXO over 200 used for a stake, so for your example, the UTXO of 1,000 coins would be spit and come back (for future staking) as two 500 QTUM UTXOs. Also, your wallet will "clean up" small transactions. If you paid the transaction fees to get really small UTXOs (0.000904 minimum for each transaction), the wallet would be likely to combine a bunch of these little UTXOs when you get a block reward, and move you back toward that 200 QTUM size.
