Please help me choose a mobo for ryzen

Here's to help you compare the 4 motherboards you are choosing from so that you can make an informed decision on which to buy:
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║ ║B║ POWER |MOS-| 2- ║ RAM ║SATA3|E║ ║ M.2[KEY-M] ║ PCI-E x16 SLOTS & MAX. SPEEDS |ADD'L║PCI║ |RJ45@REAR║ AUDIO SP|J║BUTTONS║P║ USB @ REAR U║HEADERS@MIDBOARD║RGB LED║ BUTTONS @ ║ARMOR║SIZE║PCB &║
║ BRAND / ║I║PHASE|ATX|FET |DIGIT║Q┌---╫-----┤X║U╟--┬---┬-------------╫--┬---┬--------Note:--------┬---┴-┐GPU║ -E║ WIFI ├---------╢ @REAR |D|A║ @REAR ║S╟---┬---┬---┐S║USB|USB|USB║FAN/║ STRIP ║ MIDBOARD ║ @ ║Ht.x║ACCNT║
║ MODEL ║O║(CPU |12V|HEAT|DEBUG║T|RE-║(Qty.|P║2║QT|HT.| MAX. SPEEDS ║QT|RE-|* or ^ means bndwidth|MULTI|12V║2.0║ /BT | LAN ╟-------┤I|C║CL FLSH║/║TOT|3.1|3.0|B║3.1|3.0|2.0║PUMP║HEADERS╟---┬---┬---╢I/O &║Wdth║+ LED║REF.
║ ║S║+SoC)|PIN|SINK| CODE║Y|INF║@90°)|R║ ║ Y|SNK| ║ Y|INF|shared w/ other slots| GPU |PWR║ x1║ |CNTROLLER║ CODEC |F|K║CMOS BK║2║QTY|C|A|C|A|2║ C |19p|9-p║4pin║12v|+5v║PWR|RST| OC║AUDIO║(mm)║COLOR║LINKS:
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║Asus ROG Strix║ ║ 8 | | | ║ | ║ 6x | ║ ║ | | ║ | |2x PCIe3.0 + | | ║ ║ | ║Supr.FX| | ║ | ║ ║ | | | | | ║ | | ║ 6x*║ | ║ | | ║ ║ ATX║BK/GY║Asus ROG Strix B350-F Gaming
║B350-F Gaming ║1║ (4 |1x8|ALL | X ║4| X ║(ALL)|-║-║1x| X |1x PCIe3.0x4 ║3x|2/3|1x PCIe2.0* |2w-CF| - ║ 3*║ None |1x I211AT║ S1220A|1|5║ - | - ║-║ 8x|0|2|0|4|2║ 0 | 1 | 2 ║*4x=║ 2 | - ║ - | - | - ║ X ║305x║ + ║WEBSITE
║ ║ ║+2+2)| | | ║ | ║2=CPU| ║ ║ | | ║ | |x16/-/x4*, x8/x4/x4* | | ║ ║ | ║ | | ║ | ║ ║ | | | | | ║ | | ║5VDC║ | ║ | | ║ ║ 244║ RGB ║MANUAL (E13031, 2nd Ed., May 2017, 2017/06/06 update)
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║Msi X370 ║ ║ 10 | | |Onbrd║ | ║ 6x | ║ ║ | | ║ | |2x PCIe3.0 + |2wSLI| ║ ║ | ║ | | ║ | ║ ║ | | | | | ║ | 2 | ║ ║ | ║ | | ║ ║ ATX║BK/RD║Msi X370 Gaming Plus
║Gaming Plus ║1║(4x2 |1x8|ALL | LEDs║4| X ║(ALL)|-║-║1x| X |1x PCIe3.0x4 ║3x|2/3|1x PCIe2.0* | or | - ║ 3*║ None |1x 8111H ║ ALC892|-|6║ - | - ║1║ 8x|1|1|0|4|2║ 0 |*1@| 2 ║ 6x ║ 1 | - ║ - | - | - ║ X ║305x║+ Red║WEBSITE
║ ║ ║ +2) | | | only║ | ║ | ║ ║ | | ║ | |x16/-/x4*, x8/x8/x4* |3w-CF| ║ ║ | ║ | | ║ | ║ ║ | | | | | ║ |90°| ║ ║ | ║ | | ║ ║ 244║Trace║MANUAL (E7A33v3.0, 2017/03)
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║Asus Prime ║ ║ 6 | | | ║ | ║ 6x | ║ ║ | | ║ | |1x PCIe3.0 + | | ║ ║ | ║ | | ║ | ║ ║ | | | | | ║ | | ║ ║ | ║ | | ║ ║ ATX║BK/RD║Asus Prime B350-Plus
║B350-Plus ║1║ (4 |1x8|ALL | X ║4| X ║(2/6)|-║-║1x| X |1x PCIe3.0x4 ║2x| X |1x PCIe2.0* |2w-CF| - ║ 2*║ None |1x 8111H ║ ALC887|-|3║ - | - ║1║ 8x|0|2|0|4|2║ 0 | 1 | 2 ║ 3x ║ 1*| - ║ - | - | - ║ X ║305x║+ Red║WEBSITE
║ ║ ║ +2) | | | ║ | ║ | ║ ║ | | ║ | |x16/x4* | | (+2PCI) | ║ | | ║ | ║ ║ | | | | | ║ | | ║ ║Fan| ║ | | ║ ║ 237║Trace║MANUAL (E12581, 2nd Ed., Feb.2017, 2017/03/29 update)
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║Msi B350 ║ ║ 6 | | |Onbrd║ | ║ 4x | ║ ║ | | ║ | |1x PCIe3.0 + | | ║ ║ | ║ | | ║ | ║ ║ | | | | | ║ | 2 | ║ ║ | ║ | | ║ ║ ATX║BK/RD║Msi B350 Gaming Plus
║Gaming Plus ║1║ (4 |1x8|ALL | LEDs║4| X ║(2/4)|-║-║1x| X |1x PCIe3.0x4 ║2x|1/2|1x PCIe2.0* |2w-CF| - ║ 2*║ None |1x 8111H ║ ALC892|-|6║ - | - ║1║ 6x|0|0|1|3|2║ 0 |*1@| 2 ║ 6x ║ 1 | - ║ - | - | - ║ X ║305x║+ Red║WEBSITE
║ ║ ║ +2) | | | only║ | ║ | ║ ║ | | ║ | |x16/x4* | | (+2PCI) | ║ | | ║ | ║ ║ | | | | | ║ |90°| ║ ║ | ║ | | ║ ║ 244║Trace║MANUAL (E7A34v4.0, 2017/03, 1st release)
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The best features of the Asus ROG Strix B350-F Gaming are its LAN controller (Intel I211AT), Audio (Realtek ALC1220 with Supreme FX), number of SATA ports (at 6x), number of PCIe slots (at 3x, with 2 reinforced, but only supports 2-way CrossFire and not SLI), number of fan headers (at 6x, but 4 are non-PWM), number of RGB LED Strip headers (at 2x), and on-board RGB lighting and a neutral gray color PCB.

The Msi X370 Gaming Plus have a slightly lower-tiered LAN controller (Realtek RTL8111H) and Audio Codec (Realtek ALC892), but its PCIe slots support 2-way SLI, has an additional USB3.0 header, but only 1 RGB LED Strip header and has a Black+Red theme with Red LED lighting (which, depends on your preferences of colors, might not suit your tastes).

The Asus Prime B350-Plus and the Msi B350 Gaming Plus have more disadvantages (SATA ports, PCIe slots, LAN and Audio). Both of these boards also have a Black+Red color scheme and Red LED lighting (similar to the Msi X370 Gaming Plus).

If you compare other X370 motherboards with the Msi X370 Gaming Plus, that motherboard would be somewhere in the bottom of the list (can be categorized as mainstream/mid-range X370 mobo) due to the lack of features it has compared with other X370 mobos.

If you compare other B350 motherboards with the Asus ROG Strix B350-F Gaming, that motherboard would be somewhere in the top of the list (can be categorized as high-end performance B350 mobo) due to the features it offers compared with other B350 mobos.

It's up to you which features/ports/connectivity/aesthetics you need and want.